Module: Kernel (Ruby 2.3.4)

    In Files

    • complex.c
    • cont.c
    • error.c
    • eval.c
    • eval_jump.c
    • file.c
    • io.c
    • load.c
    • object.c
    • proc.c
    • process.c
    • random.c
    • rational.c
    • ruby.c
    • signal.c
    • vm_backtrace.c
    • vm_eval.c
    • vm_trace.c

    Class/Module Index [+]

    Quicksearch

    Kernel

    The Kernel module is included by class Object, so its methods are available in every Ruby object.

    The Kernel instance methods are documented in class Object while the module methods are documented here. These methods are called without a receiver and thus can be called in functional form:

    sprintf "%.1f", 1.234 #=> "1.2"
    

    Public Instance Methods

    Array(arg) → array click to toggle source

    Returns arg as an Array.

    First tries to call to_ary on arg, then to_a.

    Array(1..5)   #=> [1, 2, 3, 4, 5]
    
     
                   static VALUE
    rb_f_array(VALUE obj, VALUE arg)
    {
        return rb_Array(arg);
    }
                
    Complex(x[, y]) → numeric click to toggle source

    Returns x+i*y;

    Complex(1, 2)    #=> (1+2i)
    Complex('1+2i')  #=> (1+2i)
    Complex(nil)     #=> TypeError
    Complex(1, nil)  #=> TypeError
    

    Syntax of string form:

    string form = extra spaces , complex , extra spaces ;
    complex = real part | [ sign ] , imaginary part
            | real part , sign , imaginary part
            | rational , "@" , rational ;
    real part = rational ;
    imaginary part = imaginary unit | unsigned rational , imaginary unit ;
    rational = [ sign ] , unsigned rational ;
    unsigned rational = numerator | numerator , "/" , denominator ;
    numerator = integer part | fractional part | integer part , fractional part ;
    denominator = digits ;
    integer part = digits ;
    fractional part = "." , digits , [ ( "e" | "E" ) , [ sign ] , digits ] ;
    imaginary unit = "i" | "I" | "j" | "J" ;
    sign = "-" | "+" ;
    digits = digit , { digit | "_" , digit };
    digit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" ;
    extra spaces = ? \s* ? ;

    See String#to_c.

     
                   static VALUE
    nucomp_f_complex(int argc, VALUE *argv, VALUE klass)
    {
        return rb_funcall2(rb_cComplex, id_convert, argc, argv);
    }
                
    Float(p1) click to toggle source
     
                   static VALUE rb_f_float(VALUE obj, VALUE arg))
                
    Hash(arg) → hash click to toggle source

    Converts arg to a Hash by calling arg.to_hash. Returns an empty Hash when arg is nil or [].

    Hash([])          #=> {}
    Hash(nil)         #=> {}
    Hash(key: :value) #=> {:key => :value}
    Hash([1, 2, 3])   #=> TypeError
    
     
                   static VALUE
    rb_f_hash(VALUE obj, VALUE arg)
    {
        return rb_Hash(arg);
    }
                
    Integer(arg, base=0) → integer click to toggle source

    Converts arg to a Fixnum or Bignum. Numeric types are converted directly (with floating point numbers being truncated). base (0, or between 2 and 36) is a base for integer string representation. If arg is a String, when base is omitted or equals zero, radix indicators (0, 0b, and 0x) are honored. In any case, strings should be strictly conformed to numeric representation. This behavior is different from that of String#to_i. Non string values will be converted by first trying to_int, then to_i. Passing nil raises a TypeError.

    Integer(123.999)    #=> 123
    Integer("0x1a")     #=> 26
    Integer(Time.new)   #=> 1204973019
    Integer("0930", 10) #=> 930
    Integer("111", 2)   #=> 7
    Integer(nil)        #=> TypeError
    
     
                   static VALUE
    rb_f_integer(int argc, VALUE *argv, VALUE obj)
    {
        VALUE arg = Qnil;
        int base = 0;
    
        switch (argc) {
          case 2:
            base = NUM2INT(argv[1]);
          case 1:
            arg = argv[0];
            break;
          default:
            /* should cause ArgumentError */
            rb_scan_args(argc, argv, "11", NULL, NULL);
        }
        return rb_convert_to_integer(arg, base);
    }
                
    Rational(x[, y]) → numeric click to toggle source

    Returns x/y;

    Rational(1, 2)   #=> (1/2)
    Rational('1/2')  #=> (1/2)
    Rational(nil)    #=> TypeError
    Rational(1, nil) #=> TypeError
    

    Syntax of string form:

    string form = extra spaces , rational , extra spaces ;
    rational = [ sign ] , unsigned rational ;
    unsigned rational = numerator | numerator , "/" , denominator ;
    numerator = integer part | fractional part | integer part , fractional part ;
    denominator = digits ;
    integer part = digits ;
    fractional part = "." , digits , [ ( "e" | "E" ) , [ sign ] , digits ] ;
    sign = "-" | "+" ;
    digits = digit , { digit | "_" , digit } ;
    digit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" ;
    extra spaces = ? \s* ? ;

    See String#to_r.

     
                   static VALUE
    nurat_f_rational(int argc, VALUE *argv, VALUE klass)
    {
        return rb_funcall2(rb_cRational, id_convert, argc, argv);
    }
                
    String(arg) → string click to toggle source

    Returns arg as a String.

    First tries to call its to_str method, then its to_s method.

    String(self)        #=> "main"
    String(self.class)  #=> "Object"
    String(123456)      #=> "123456"
    
     
                   static VALUE
    rb_f_string(VALUE obj, VALUE arg)
    {
        return rb_String(arg);
    }
                
    __callee__ → symbol click to toggle source

    Returns the called name of the current method as a Symbol. If called outside of a method, it returns nil.

     
                   static VALUE
    rb_f_callee_name(void)
    {
        ID fname = prev_frame_callee(); /* need *callee* ID */
    
        if (fname) {
            return ID2SYM(fname);
        }
        else {
            return Qnil;
        }
    }
                
    __dir__ → string click to toggle source

    Returns the canonicalized absolute path of the directory of the file from which this method is called. It means symlinks in the path is resolved. If __FILE__ is nil, it returns nil. The return value equals to File.dirname(File.realpath(__FILE__)).

     
                   static VALUE
    f_current_dirname(void)
    {
        VALUE base = rb_current_realfilepath();
        if (NIL_P(base)) {
            return Qnil;
        }
        base = rb_file_dirname(base);
        return base;
    }
                
    __method__ → symbol click to toggle source

    Returns the name at the definition of the current method as a Symbol. If called outside of a method, it returns nil.

     
                   static VALUE
    rb_f_method_name(void)
    {
        ID fname = prev_frame_func(); /* need *method* ID */
    
        if (fname) {
            return ID2SYM(fname);
        }
        else {
            return Qnil;
        }
    }
                
    `cmd` → string click to toggle source

    Returns the standard output of running cmd in a subshell. The built-in syntax %x{...} uses this method. Sets $? to the process status.

    %x`date`                   #=> "Wed Apr  9 08:56:30 CDT 2003\n"
    %x`ls testdir`.split[1]    #=> "main.rb"
    %x`echo oops && exit 99`   #=> "oops\n"
    $?.exitstatus            #=> 99
    
     
                   static VALUE
    rb_f_backquote(VALUE obj, VALUE str)
    {
        VALUE port;
        VALUE result;
        rb_io_t *fptr;
    
        SafeStringValue(str);
        rb_last_status_clear();
        port = pipe_open_s(str, "r", FMODE_READABLE|DEFAULT_TEXTMODE, NULL);
        if (NIL_P(port)) return rb_str_new(0,0);
    
        GetOpenFile(port, fptr);
        result = read_all(fptr, remain_size(fptr), Qnil);
        rb_io_close(port);
        rb_io_fptr_finalize(fptr);
        rb_gc_force_recycle(port); /* also guards from premature GC */
    
        return result;
    }
                
    abort click to toggle source
    Kernel::abort([msg])
    Process::abort([msg])

    Terminate execution immediately, effectively by calling Kernel.exit(false). If msg is given, it is written to STDERR prior to terminating.

     
                   VALUE
    rb_f_abort(int argc, const VALUE *argv)
    {
        rb_check_arity(argc, 0, 1);
        if (argc == 0) {
            if (!NIL_P(GET_THREAD()->errinfo)) {
                ruby_error_print();
            }
            rb_exit(EXIT_FAILURE);
        }
        else {
            VALUE args[2];
    
            args[1] = args[0] = argv[0];
            StringValue(args[0]);
            rb_io_puts(1, args, rb_stderr);
            args[0] = INT2NUM(EXIT_FAILURE);
            rb_exc_raise(rb_class_new_instance(2, args, rb_eSystemExit));
        }
    
        UNREACHABLE;
    }
                
    at_exit { block } → proc click to toggle source

    Converts block to a Proc object (and therefore binds it at the point of call) and registers it for execution when the program exits. If multiple handlers are registered, they are executed in reverse order of registration.

    def do_at_exit(str1)
      at_exit { print str1 }
    end
    at_exit { puts "cruel world" }
    do_at_exit("goodbye ")
    exit
    

    produces:

    goodbye cruel world
    
     
                   static VALUE
    rb_f_at_exit(void)
    {
        VALUE proc;
    
        if (!rb_block_given_p()) {
            rb_raise(rb_eArgError, "called without a block");
        }
        proc = rb_block_proc();
        rb_set_end_proc(rb_call_end_proc, proc);
        return proc;
    }
                
    autoload(module, filename) → nil click to toggle source

    Registers filename to be loaded (using Kernel::require) the first time that module (which may be a String or a symbol) is accessed.

    autoload(:MyModule, "/usr/local/lib/modules/my_module.rb")
    
     
                   static VALUE
    rb_f_autoload(VALUE obj, VALUE sym, VALUE file)
    {
        VALUE klass = rb_class_real(rb_vm_cbase());
        if (NIL_P(klass)) {
            rb_raise(rb_eTypeError, "Can not set autoload on singleton class");
        }
        return rb_mod_autoload(klass, sym, file);
    }
                
    autoload?(name) → String or nil click to toggle source

    Returns filename to be loaded if name is registered as autoload.

    autoload(:B, "b")
    autoload?(:B)            #=> "b"
    
     
                   static VALUE
    rb_f_autoload_p(VALUE obj, VALUE sym)
    {
        /* use rb_vm_cbase() as same as rb_f_autoload. */
        VALUE klass = rb_vm_cbase();
        if (NIL_P(klass)) {
            return Qnil;
        }
        return rb_mod_autoload_p(klass, sym);
    }
                
    binding → a_binding click to toggle source

    Returns a Binding object, describing the variable and method bindings at the point of call. This object can be used when calling eval to execute the evaluated command in this environment. See also the description of class Binding.

    def get_binding(param)
      binding
    end
    b = get_binding("hello")
    eval("param", b)   #=> "hello"
    
     
                   static VALUE
    rb_f_binding(VALUE self)
    {
        return rb_binding_new();
    }
                
    block_given? → true or false click to toggle source

    Returns true if yield would execute a block in the current context. The iterator? form is mildly deprecated.

    def try
      if block_given?
        yield
      else
        "no block"
      end
    end
    try                  #=> "no block"
    try { "hello" }      #=> "hello"
    try do "hello" end   #=> "hello"
    
     
                   VALUE
    rb_f_block_given_p(void)
    {
        rb_thread_t *th = GET_THREAD();
        rb_control_frame_t *cfp = th->cfp;
        cfp = vm_get_ruby_level_caller_cfp(th, RUBY_VM_PREVIOUS_CONTROL_FRAME(cfp));
    
        if (cfp != 0 && VM_CF_BLOCK_PTR(cfp)) {
            return Qtrue;
        }
        else {
            return Qfalse;
        }
    }
                
    callcc {|cont| block } → obj click to toggle source

    Generates a Continuation object, which it passes to the associated block. You need to require 'continuation' before using this method. Performing a cont.call will cause the callcc to return (as will falling through the end of the block). The value returned by the callcc is the value of the block, or the value passed to cont.call. See class Continuation for more details. Also see #throw for an alternative mechanism for unwinding a call stack.

     
                   static VALUE
    rb_callcc(VALUE self)
    {
        volatile int called;
        volatile VALUE val = cont_capture(&called);
    
        if (called) {
            return val;
        }
        else {
            return rb_yield(val);
        }
    }
                
    caller(start=1, length=nil) → array or nil click to toggle source
    caller(range) → array or nil

    Returns the current execution stack—an array containing strings in the form file:line or file:line: in `method'.

    The optional start parameter determines the number of initial stack entries to omit from the top of the stack.

    A second optional length parameter can be used to limit how many entries are returned from the stack.

    Returns nil if start is greater than the size of current execution stack.

    Optionally you can pass a range, which will return an array containing the entries within the specified range.

    def a(skip)
      caller(skip)
    end
    def b(skip)
      a(skip)
    end
    def c(skip)
      b(skip)
    end
    c(0)   #=> ["prog:2:in `a'", "prog:5:in `b'", "prog:8:in `c'", "prog:10:in `<main>'"]
    c(1)   #=> ["prog:5:in `b'", "prog:8:in `c'", "prog:11:in `<main>'"]
    c(2)   #=> ["prog:8:in `c'", "prog:12:in `<main>'"]
    c(3)   #=> ["prog:13:in `<main>'"]
    c(4)   #=> []
    c(5)   #=> nil
    
     
                   static VALUE
    rb_f_caller(int argc, VALUE *argv)
    {
        return vm_backtrace_to_ary(GET_THREAD(), argc, argv, 1, 1, 1);
    }
                
    caller_locations(start=1, length=nil) → array or nil click to toggle source
    caller_locations(range) → array or nil

    Returns the current execution stack—an array containing backtrace location objects.

    See Thread::Backtrace::Location for more information.

    The optional start parameter determines the number of initial stack entries to omit from the top of the stack.

    A second optional length parameter can be used to limit how many entries are returned from the stack.

    Returns nil if start is greater than the size of current execution stack.

    Optionally you can pass a range, which will return an array containing the entries within the specified range.

     
                   static VALUE
    rb_f_caller_locations(int argc, VALUE *argv)
    {
        return vm_backtrace_to_ary(GET_THREAD(), argc, argv, 1, 1, 0);
    }
                
    catch([tag]) {|tag| block } → obj click to toggle source

    catch executes its block. If throw is not called, the block executes normally, and catch returns the value of the last expression evaluated.

    catch(1) { 123 }            # => 123
    

    If throw(tag2, val) is called, Ruby searches up its stack for a catch block whose tag has the same object_id as tag2. When found, the block stops executing and returns val (or nil if no second argument was given to throw).

    catch(1) { throw(1, 456) }  # => 456
    catch(1) { throw(1) }       # => nil
    

    When tag is passed as the first argument, catch yields it as the parameter of the block.

    catch(1) {|x| x + 2 }       # => 3
    

    When no tag is given, catch yields a new unique object (as from Object.new) as the block parameter. This object can then be used as the argument to throw, and will match the correct catch block.

    catch do |obj_A|
      catch do |obj_B|
        throw(obj_B, 123)
        puts "This puts is not reached"
      end
    
      puts "This puts is displayed"
      456
    end
    
    # => 456
    
    catch do |obj_A|
      catch do |obj_B|
        throw(obj_A, 123)
        puts "This puts is still not reached"
      end
    
      puts "Now this puts is also not reached"
      456
    end
    
    # => 123
    
     
                   static VALUE
    rb_f_catch(int argc, VALUE *argv)
    {
        VALUE tag;
    
        if (argc == 0) {
            tag = rb_obj_alloc(rb_cObject);
        }
        else {
            rb_scan_args(argc, argv, "01", &tag);
        }
        return rb_catch_obj(tag, catch_i, 0);
    }
                
    chomp → $_ click to toggle source
    chomp(string) → $_

    Equivalent to $_ = $_.chomp(string). See String#chomp. Available only when -p/-n command line option specified.

     
                   static VALUE
    rb_f_chomp(int argc, VALUE *argv)
    {
        VALUE str = rb_funcall_passing_block(uscore_get(), rb_intern("chomp"), argc, argv);
        rb_lastline_set(str);
        return str;
    }
                
    chop → $_ click to toggle source

    Equivalent to ($_.dup).chop!, except nil is never returned. See String#chop!. Available only when -p/-n command line option specified.

     
                   static VALUE
    rb_f_chop(void)
    {
        VALUE str = rb_funcall_passing_block(uscore_get(), rb_intern("chop"), 0, 0);
        rb_lastline_set(str);
        return str;
    }
                
    eval(string [, binding [, filename [,lineno]]]) → obj click to toggle source

    Evaluates the Ruby expression(s) in string. If binding is given, which must be a Binding object, the evaluation is performed in its context. If the optional filename and lineno parameters are present, they will be used when reporting syntax errors.

    def get_binding(str)
      return binding
    end
    str = "hello"
    eval "str + ' Fred'"                      #=> "hello Fred"
    eval "str + ' Fred'", get_binding("bye")  #=> "bye Fred"
    
     
                   VALUE
    rb_f_eval(int argc, const VALUE *argv, VALUE self)
    {
        VALUE src, scope, vfile, vline;
        VALUE file = Qundef;
        int line = 1;
    
        rb_scan_args(argc, argv, "13", &src, &scope, &vfile, &vline);
        SafeStringValue(src);
        if (argc >= 3) {
            StringValue(vfile);
        }
        if (argc >= 4) {
            line = NUM2INT(vline);
        }
    
        if (!NIL_P(vfile))
            file = vfile;
        return eval_string(self, src, scope, file, line);
    }
                
    exec([env,] command... [,options]) click to toggle source

    Replaces the current process by running the given external command, which can take one of the following forms:

    exec(commandline)

    command line string which is passed to the standard shell

    exec(cmdname, arg1, ...)

    command name and one or more arguments (no shell)

    exec([cmdname, argv0], arg1, ...)

    command name, argv and zero or more arguments (no shell)

    In the first form, the string is taken as a command line that is subject to shell expansion before being executed.

    The standard shell always means "/bin/sh" on Unix-like systems, same as ENV["RUBYSHELL"] (or ENV["COMSPEC"] on Windows NT series), and similar.

    If the string from the first form (exec("command")) follows these simple rules:

    • no meta characters

    • no shell reserved word and no special built-in

    • Ruby invokes the command directly without shell

    You can force shell invocation by adding “;” to the string (because “;” is a meta character).

    Note that this behavior is observable by pid obtained (return value of spawn() and IO#pid for IO.popen) is the pid of the invoked command, not shell.

    In the second form (exec("command1", "arg1", ...)), the first is taken as a command name and the rest are passed as parameters to command with no shell expansion.

    In the third form (exec(["command", "argv0"], "arg1", ...)), starting a two-element array at the beginning of the command, the first element is the command to be executed, and the second argument is used as the argv[0] value, which may show up in process listings.

    In order to execute the command, one of the exec(2) system calls are used, so the running command may inherit some of the environment of the original program (including open file descriptors).

    This behavior is modified by the given env and options parameters. See ::spawn for details.

    If the command fails to execute (typically Errno::ENOENT when it was not found) a SystemCallError exception is raised.

    This method modifies process attributes according to given options before exec(2) system call. See ::spawn for more details about the given options.

    The modified attributes may be retained when exec(2) system call fails.

    For example, hard resource limits are not restorable.

    Consider to create a child process using ::spawn or #system if this is not acceptable.

    exec "echo *"       # echoes list of files in current directory
    # never get here
    
    exec "echo", "*"    # echoes an asterisk
    # never get here
    
     
                   VALUE
    rb_f_exec(int argc, const VALUE *argv)
    {
        VALUE execarg_obj, fail_str;
        struct rb_execarg *eargp;
    #define CHILD_ERRMSG_BUFLEN 80
        char errmsg[CHILD_ERRMSG_BUFLEN] = { '\0' };
        int err;
    
        execarg_obj = rb_execarg_new(argc, argv, TRUE);
        eargp = rb_execarg_get(execarg_obj);
        before_exec(); /* stop timer thread before redirects */
        rb_execarg_parent_start(execarg_obj);
        fail_str = eargp->use_shell ? eargp->invoke.sh.shell_script : eargp->invoke.cmd.command_name;
    
        rb_exec_async_signal_safe(eargp, errmsg, sizeof(errmsg));
    
        err = errno;
        after_exec(); /* restart timer thread */
    
        rb_exec_fail(eargp, err, errmsg);
        RB_GC_GUARD(execarg_obj);
        rb_syserr_fail_str(err, fail_str);
        return Qnil;                /* dummy */
    }
                
    exit(status=true) click to toggle source
    Kernel::exit(status=true)
    Process::exit(status=true)

    Initiates the termination of the Ruby script by raising the SystemExit exception. This exception may be caught. The optional parameter is used to return a status code to the invoking environment. true and FALSE of status means success and failure respectively. The interpretation of other integer values are system dependent.

    begin
      exit
      puts "never get here"
    rescue SystemExit
      puts "rescued a SystemExit exception"
    end
    puts "after begin block"
    

    produces:

    rescued a SystemExit exception
    after begin block

    Just prior to termination, Ruby executes any at_exit functions (see Kernel::at_exit) and runs any object finalizers (see ObjectSpace.define_finalizer).

    at_exit { puts "at_exit function" }
    ObjectSpace.define_finalizer("string",  proc { puts "in finalizer" })
    exit
    

    produces:

    at_exit function
    in finalizer
     
                   VALUE
    rb_f_exit(int argc, const VALUE *argv)
    {
        VALUE status;
        int istatus;
    
        if (argc > 0 && rb_scan_args(argc, argv, "01", &status) == 1) {
            istatus = exit_status_code(status);
        }
        else {
            istatus = EXIT_SUCCESS;
        }
        rb_exit(istatus);
    
        UNREACHABLE;
    }
                
    exit!(status=false) click to toggle source

    Exits the process immediately. No exit handlers are run. status is returned to the underlying system as the exit status.

    Process.exit!(true)
    
     
                   static VALUE
    rb_f_exit_bang(int argc, VALUE *argv, VALUE obj)
    {
        VALUE status;
        int istatus;
    
        if (argc > 0 && rb_scan_args(argc, argv, "01", &status) == 1) {
            istatus = exit_status_code(status);
        }
        else {
            istatus = EXIT_FAILURE;
        }
        _exit(istatus);
    
        UNREACHABLE;
    }
                
    fail click to toggle source
    fail(string)
    fail(exception [, string [, array]])

    With no arguments, raises the exception in $! or raises a RuntimeError if $! is nil. With a single String argument, raises a RuntimeError with the string as a message. Otherwise, the first parameter should be the name of an Exception class (or an object that returns an Exception object when sent an exception message). The optional second parameter sets the message associated with the exception, and the third parameter is an array of callback information. Exceptions are caught by the rescue clause of begin...end blocks.

    raise "Failed to create socket"
    raise ArgumentError, "No parameters", caller
    
     
                   static VALUE
    rb_f_raise(int argc, VALUE *argv)
    {
        VALUE err;
        VALUE opts[raise_max_opt], *const cause = &opts[raise_opt_cause];
    
        argc = extract_raise_opts(argc, argv, opts);
        if (argc == 0) {
            if (*cause != Qundef) {
                rb_raise(rb_eArgError, "only cause is given with no arguments");
            }
            err = get_errinfo();
            if (!NIL_P(err)) {
                argc = 1;
                argv = &err;
            }
        }
        rb_raise_jump(rb_make_exception(argc, argv), *cause);
    
        UNREACHABLE;
    }
                
    fork [{ block }] → fixnum or nil click to toggle source
    fork [{ block }] → fixnum or nil

    Creates a subprocess. If a block is specified, that block is run in the subprocess, and the subprocess terminates with a status of zero. Otherwise, the fork call returns twice, once in the parent, returning the process ID of the child, and once in the child, returning nil. The child process can exit using Kernel.exit! to avoid running any at_exit functions. The parent process should use Process.wait to collect the termination statuses of its children or use Process.detach to register disinterest in their status; otherwise, the operating system may accumulate zombie processes.

    The thread calling fork is the only thread in the created child process. fork doesn’t copy other threads.

    If fork is not usable, Process.respond_to?(:fork) returns false.

    Note that fork(2) is not available on some platforms like Windows and NetBSD 4. Therefore you should use spawn() instead of fork().

     
                   static VALUE
    rb_f_fork(VALUE obj)
    {
        rb_pid_t pid;
    
        switch (pid = rb_fork_ruby(NULL)) {
          case 0:
            rb_thread_atfork();
            if (rb_block_given_p()) {
                int status;
    
                rb_protect(rb_yield, Qundef, &status);
                ruby_stop(status);
            }
            return Qnil;
    
          case -1:
            rb_sys_fail("fork(2)");
            return Qnil;
    
          default:
            return PIDT2NUM(pid);
        }
    }
                
    format(format_string [, arguments...] ) → string click to toggle source

    Returns the string resulting from applying format_string to any additional arguments. Within the format string, any characters other than format sequences are copied to the result.

    The syntax of a format sequence is follows.

    %[flags][width][.precision]type

    A format sequence consists of a percent sign, followed by optional flags, width, and precision indicators, then terminated with a field type character. The field type controls how the corresponding sprintf argument is to be interpreted, while the flags modify that interpretation.

    The field type characters are:

    Field |  Integer Format
    ------+--------------------------------------------------------------
      b   | Convert argument as a binary number.
          | Negative numbers will be displayed as a two's complement
          | prefixed with `..1'.
      B   | Equivalent to `b', but uses an uppercase 0B for prefix
          | in the alternative format by #.
      d   | Convert argument as a decimal number.
      i   | Identical to `d'.
      o   | Convert argument as an octal number.
          | Negative numbers will be displayed as a two's complement
          | prefixed with `..7'.
      u   | Identical to `d'.
      x   | Convert argument as a hexadecimal number.
          | Negative numbers will be displayed as a two's complement
          | prefixed with `..f' (representing an infinite string of
          | leading 'ff's).
      X   | Equivalent to `x', but uses uppercase letters.
    
    Field |  Float Format
    ------+--------------------------------------------------------------
      e   | Convert floating point argument into exponential notation
          | with one digit before the decimal point as [-]d.dddddde[+-]dd.
          | The precision specifies the number of digits after the decimal
          | point (defaulting to six).
      E   | Equivalent to `e', but uses an uppercase E to indicate
          | the exponent.
      f   | Convert floating point argument as [-]ddd.dddddd,
          | where the precision specifies the number of digits after
          | the decimal point.
      g   | Convert a floating point number using exponential form
          | if the exponent is less than -4 or greater than or
          | equal to the precision, or in dd.dddd form otherwise.
          | The precision specifies the number of significant digits.
      G   | Equivalent to `g', but use an uppercase `E' in exponent form.
      a   | Convert floating point argument as [-]0xh.hhhhp[+-]dd,
          | which is consisted from optional sign, "0x", fraction part
          | as hexadecimal, "p", and exponential part as decimal.
      A   | Equivalent to `a', but use uppercase `X' and `P'.
    
    Field |  Other Format
    ------+--------------------------------------------------------------
      c   | Argument is the numeric code for a single character or
          | a single character string itself.
      p   | The valuing of argument.inspect.
      s   | Argument is a string to be substituted.  If the format
          | sequence contains a precision, at most that many characters
          | will be copied.
      %   | A percent sign itself will be displayed.  No argument taken.

    The flags modifies the behavior of the formats. The flag characters are:

    Flag     | Applies to    | Meaning
    ---------+---------------+-----------------------------------------
    space    | bBdiouxX      | Leave a space at the start of
             | aAeEfgG       | non-negative numbers.
             | (numeric fmt) | For `o', `x', `X', `b' and `B', use
             |               | a minus sign with absolute value for
             |               | negative values.
    ---------+---------------+-----------------------------------------
    (digit)$ | all           | Specifies the absolute argument number
             |               | for this field.  Absolute and relative
             |               | argument numbers cannot be mixed in a
             |               | sprintf string.
    ---------+---------------+-----------------------------------------
     #       | bBoxX         | Use an alternative format.
             | aAeEfgG       | For the conversions `o', increase the precision
             |               | until the first digit will be `0' if
             |               | it is not formatted as complements.
             |               | For the conversions `x', `X', `b' and `B'
             |               | on non-zero, prefix the result with ``0x'',
             |               | ``0X'', ``0b'' and ``0B'', respectively.
             |               | For `a', `A', `e', `E', `f', `g', and 'G',
             |               | force a decimal point to be added,
             |               | even if no digits follow.
             |               | For `g' and 'G', do not remove trailing zeros.
    ---------+---------------+-----------------------------------------
    +        | bBdiouxX      | Add a leading plus sign to non-negative
             | aAeEfgG       | numbers.
             | (numeric fmt) | For `o', `x', `X', `b' and `B', use
             |               | a minus sign with absolute value for
             |               | negative values.
    ---------+---------------+-----------------------------------------
    -        | all           | Left-justify the result of this conversion.
    ---------+---------------+-----------------------------------------
    0 (zero) | bBdiouxX      | Pad with zeros, not spaces.
             | aAeEfgG       | For `o', `x', `X', `b' and `B', radix-1
             | (numeric fmt) | is used for negative numbers formatted as
             |               | complements.
    ---------+---------------+-----------------------------------------
    *        | all           | Use the next argument as the field width.
             |               | If negative, left-justify the result. If the
             |               | asterisk is followed by a number and a dollar
             |               | sign, use the indicated argument as the width.

    Examples of flags:

    # `+' and space flag specifies the sign of non-negative numbers.
    sprintf("%d", 123)  #=> "123"
    sprintf("%+d", 123) #=> "+123"
    sprintf("% d", 123) #=> " 123"
    
    # `#' flag for `o' increases number of digits to show `0'.
    # `+' and space flag changes format of negative numbers.
    sprintf("%o", 123)   #=> "173"
    sprintf("%#o", 123)  #=> "0173"
    sprintf("%+o", -123) #=> "-173"
    sprintf("%o", -123)  #=> "..7605"
    sprintf("%#o", -123) #=> "..7605"
    
    # `#' flag for `x' add a prefix `0x' for non-zero numbers.
    # `+' and space flag disables complements for negative numbers.
    sprintf("%x", 123)   #=> "7b"
    sprintf("%#x", 123)  #=> "0x7b"
    sprintf("%+x", -123) #=> "-7b"
    sprintf("%x", -123)  #=> "..f85"
    sprintf("%#x", -123) #=> "0x..f85"
    sprintf("%#x", 0)    #=> "0"
    
    # `#' for `X' uses the prefix `0X'.
    sprintf("%X", 123)  #=> "7B"
    sprintf("%#X", 123) #=> "0X7B"
    
    # `#' flag for `b' add a prefix `0b' for non-zero numbers.
    # `+' and space flag disables complements for negative numbers.
    sprintf("%b", 123)   #=> "1111011"
    sprintf("%#b", 123)  #=> "0b1111011"
    sprintf("%+b", -123) #=> "-1111011"
    sprintf("%b", -123)  #=> "..10000101"
    sprintf("%#b", -123) #=> "0b..10000101"
    sprintf("%#b", 0)    #=> "0"
    
    # `#' for `B' uses the prefix `0B'.
    sprintf("%B", 123)  #=> "1111011"
    sprintf("%#B", 123) #=> "0B1111011"
    
    # `#' for `e' forces to show the decimal point.
    sprintf("%.0e", 1)  #=> "1e+00"
    sprintf("%#.0e", 1) #=> "1.e+00"
    
    # `#' for `f' forces to show the decimal point.
    sprintf("%.0f", 1234)  #=> "1234"
    sprintf("%#.0f", 1234) #=> "1234."
    
    # `#' for `g' forces to show the decimal point.
    # It also disables stripping lowest zeros.
    sprintf("%g", 123.4)   #=> "123.4"
    sprintf("%#g", 123.4)  #=> "123.400"
    sprintf("%g", 123456)  #=> "123456"
    sprintf("%#g", 123456) #=> "123456."
    

    The field width is an optional integer, followed optionally by a period and a precision. The width specifies the minimum number of characters that will be written to the result for this field.

    Examples of width:

    # padding is done by spaces,       width=20
    # 0 or radix-1.             <------------------>
    sprintf("%20d", 123)   #=> "                 123"
    sprintf("%+20d", 123)  #=> "                +123"
    sprintf("%020d", 123)  #=> "00000000000000000123"
    sprintf("%+020d", 123) #=> "+0000000000000000123"
    sprintf("% 020d", 123) #=> " 0000000000000000123"
    sprintf("%-20d", 123)  #=> "123                 "
    sprintf("%-+20d", 123) #=> "+123                "
    sprintf("%- 20d", 123) #=> " 123                "
    sprintf("%020x", -123) #=> "..ffffffffffffffff85"
    

    For numeric fields, the precision controls the number of decimal places displayed. For string fields, the precision determines the maximum number of characters to be copied from the string. (Thus, the format sequence %10.10s will always contribute exactly ten characters to the result.)

    Examples of precisions:

    # precision for `d', 'o', 'x' and 'b' is
    # minimum number of digits               <------>
    sprintf("%20.8d", 123)  #=> "            00000123"
    sprintf("%20.8o", 123)  #=> "            00000173"
    sprintf("%20.8x", 123)  #=> "            0000007b"
    sprintf("%20.8b", 123)  #=> "            01111011"
    sprintf("%20.8d", -123) #=> "           -00000123"
    sprintf("%20.8o", -123) #=> "            ..777605"
    sprintf("%20.8x", -123) #=> "            ..ffff85"
    sprintf("%20.8b", -11)  #=> "            ..110101"
    
    # "0x" and "0b" for `#x' and `#b' is not counted for
    # precision but "0" for `#o' is counted.  <------>
    sprintf("%#20.8d", 123)  #=> "            00000123"
    sprintf("%#20.8o", 123)  #=> "            00000173"
    sprintf("%#20.8x", 123)  #=> "          0x0000007b"
    sprintf("%#20.8b", 123)  #=> "          0b01111011"
    sprintf("%#20.8d", -123) #=> "           -00000123"
    sprintf("%#20.8o", -123) #=> "            ..777605"
    sprintf("%#20.8x", -123) #=> "          0x..ffff85"
    sprintf("%#20.8b", -11)  #=> "          0b..110101"
    
    # precision for `e' is number of
    # digits after the decimal point           <------>
    sprintf("%20.8e", 1234.56789) #=> "      1.23456789e+03"
    
    # precision for `f' is number of
    # digits after the decimal point               <------>
    sprintf("%20.8f", 1234.56789) #=> "       1234.56789000"
    
    # precision for `g' is number of
    # significant digits                          <------->
    sprintf("%20.8g", 1234.56789) #=> "           1234.5679"
    
    #                                         <------->
    sprintf("%20.8g", 123456789)  #=> "       1.2345679e+08"
    
    # precision for `s' is
    # maximum number of characters                    <------>
    sprintf("%20.8s", "string test") #=> "            string t"
    

    Examples:

    sprintf("%d %04x", 123, 123)               #=> "123 007b"
    sprintf("%08b '%4s'", 123, 123)            #=> "01111011 ' 123'"
    sprintf("%1$*2$s %2$d %1$s", "hello", 8)   #=> "   hello 8 hello"
    sprintf("%1$*2$s %2$d", "hello", -8)       #=> "hello    -8"
    sprintf("%+g:% g:%-g", 1.23, 1.23, 1.23)   #=> "+1.23: 1.23:1.23"
    sprintf("%u", -123)                        #=> "-123"
    

    For more complex formatting, Ruby supports a reference by name. %<name>s style uses format style, but %{name} style doesn't.

    Examples:

    sprintf("%<foo>d : %<bar>f", { :foo => 1, :bar => 2 })
      #=> 1 : 2.000000
    sprintf("%{foo}f", { :foo => 1 })
      # => "1f"
    
     
                   VALUE
    rb_f_sprintf(int argc, const VALUE *argv)
    {
        return rb_str_format(argc - 1, argv + 1, GETNTHARG(0));
    }
                
    gets(sep=$/) → string or nil click to toggle source
    gets(limit) → string or nil
    gets(sep, limit) → string or nil

    Returns (and assigns to $_) the next line from the list of files in ARGV (or $*), or from standard input if no files are present on the command line. Returns nil at end of file. The optional argument specifies the record separator. The separator is included with the contents of each record. A separator of nil reads the entire contents, and a zero-length separator reads the input one paragraph at a time, where paragraphs are divided by two consecutive newlines. If the first argument is an integer, or optional second argument is given, the returning string would not be longer than the given value in bytes. If multiple filenames are present in ARGV, gets(nil) will read the contents one file at a time.

    ARGV << "testfile"
    print while gets
    

    produces:

    This is line one
    This is line two
    This is line three
    And so on...

    The style of programming using $_ as an implicit parameter is gradually losing favor in the Ruby community.

     
                   static VALUE
    rb_f_gets(int argc, VALUE *argv, VALUE recv)
    {
        if (recv == argf) {
            return argf_gets(argc, argv, argf);
        }
        return rb_funcall2(argf, idGets, argc, argv);
    }
                
    global_variables → array click to toggle source

    Returns an array of the names of global variables.

    global_variables.grep /std/   #=> [:$stdin, :$stdout, :$stderr]
    
     
                   VALUE
    rb_f_global_variables(void)
    {
        VALUE ary = rb_ary_new();
        char buf[2];
        int i;
    
        rb_id_table_foreach(rb_global_tbl, gvar_i, (void *)ary);
        buf[0] = '$';
        for (i = 1; i <= 9; ++i) {
    	buf[1] = (char)(i + '0');
    	rb_ary_push(ary, ID2SYM(rb_intern2(buf, 2)));
        }
        return ary;
    }
                
    gsub(pattern, replacement) → $_ click to toggle source
    gsub(pattern) {|...| block } → $_

    Equivalent to $_.gsub..., except that $_ will be updated if substitution occurs. Available only when -p/-n command line option specified.

     
                   static VALUE
    rb_f_gsub(int argc, VALUE *argv)
    {
        VALUE str = rb_funcall_passing_block(uscore_get(), rb_intern("gsub"), argc, argv);
        rb_lastline_set(str);
        return str;
    }
                
    iterator? → true or false click to toggle source

    Returns true if yield would execute a block in the current context. The iterator? form is mildly deprecated.

    def try
      if block_given?
        yield
      else
        "no block"
      end
    end
    try                  #=> "no block"
    try { "hello" }      #=> "hello"
    try do "hello" end   #=> "hello"
    
     
                   VALUE
    rb_f_block_given_p(void)
    {
        rb_thread_t *th = GET_THREAD();
        rb_control_frame_t *cfp = th->cfp;
        cfp = vm_get_ruby_level_caller_cfp(th, RUBY_VM_PREVIOUS_CONTROL_FRAME(cfp));
    
        if (cfp != 0 && VM_CF_BLOCK_PTR(cfp)) {
            return Qtrue;
        }
        else {
            return Qfalse;
        }
    }
                
    lambda { |...| block } → a_proc click to toggle source

    Equivalent to Proc.new, except the resulting Proc objects check the number of parameters passed when called.

     
                   VALUE
    rb_block_lambda(void)
    {
        return proc_new(rb_cProc, TRUE);
    }
                
    load(filename, wrap=false) → true click to toggle source

    Loads and executes the Ruby program in the file filename. If the filename does not resolve to an absolute path, the file is searched for in the library directories listed in $:. If the optional wrap parameter is true, the loaded script will be executed under an anonymous module, protecting the calling program’s global namespace. In no circumstance will any local variables in the loaded file be propagated to the loading environment.

     
                   static VALUE
    rb_f_load(int argc, VALUE *argv)
    {
        VALUE fname, wrap, path, orig_fname;
    
        rb_scan_args(argc, argv, "11", &fname, &wrap);
    
        RUBY_DTRACE_HOOK(LOAD_ENTRY, StringValuePtr(fname));
    
        orig_fname = FilePathValue(fname);
        fname = rb_str_encode_ospath(orig_fname);
        path = rb_find_file(fname);
        if (!path) {
            if (!rb_file_load_ok(RSTRING_PTR(fname)))
                load_failed(orig_fname);
            path = fname;
        }
        rb_load_internal(path, RTEST(wrap));
    
        RUBY_DTRACE_HOOK(LOAD_RETURN, StringValuePtr(fname));
    
        return Qtrue;
    }
                
    local_variables → array click to toggle source

    Returns the names of the current local variables.

    fred = 1
    for i in 1..10
       # ...
    end
    local_variables   #=> [:fred, :i]
    
     
                   static VALUE
    rb_f_local_variables(void)
    {
        struct local_var_list vars;
        rb_thread_t *th = GET_THREAD();
        rb_control_frame_t *cfp =
            vm_get_ruby_level_caller_cfp(th, RUBY_VM_PREVIOUS_CONTROL_FRAME(th->cfp));
        unsigned int i;
    
        local_var_list_init(&vars);
        while (cfp) {
            if (cfp->iseq) {
                for (i = 0; i < cfp->iseq->body->local_table_size; i++) {
                    local_var_list_add(&vars, cfp->iseq->body->local_table[i]);
                }
            }
            if (!VM_EP_LEP_P(cfp->ep)) {
                /* block */
                VALUE *ep = VM_CF_PREV_EP(cfp);
    
                if (vm_collect_local_variables_in_heap(th, ep, &vars)) {
                    break;
                }
                else {
                    while (cfp->ep != ep) {
                        cfp = RUBY_VM_PREVIOUS_CONTROL_FRAME(cfp);
                    }
                }
            }
            else {
                break;
            }
        }
        return local_var_list_finish(&vars);
    }
                
    loop { block } click to toggle source
    loop → an_enumerator

    Repeatedly executes the block.

    If no block is given, an enumerator is returned instead.

    loop do
      print "Input: "
      line = gets
      break if !line or line =~ /^qQ/
      # ...
    end
    

    StopIteration raised in the block breaks the loop. In this case, loop returns the "result" value stored in the exception.

    enum = Enumerator.new { |y|
      y << "one"
      y << "two"
      :ok
    }
    
    result = loop {
      puts enum.next
    } #=> :ok
    
     
                   static VALUE
    rb_f_loop(VALUE self)
    {
        RETURN_SIZED_ENUMERATOR(self, 0, 0, rb_f_loop_size);
        return rb_rescue2(loop_i, (VALUE)0, loop_stop, (VALUE)0, rb_eStopIteration, (VALUE)0);
    }
                
    open(path [, mode [, perm]] [, opt]) → io or nil click to toggle source
    open(path [, mode [, perm]] [, opt]) {|io| block } → obj

    Creates an IO object connected to the given stream, file, or subprocess.

    If path does not start with a pipe character (|), treat it as the name of a file to open using the specified mode (defaulting to “r”).

    The mode is either a string or an integer. If it is an integer, it must be bitwise-or of open(2) flags, such as File::RDWR or File::EXCL. If it is a string, it is either “fmode”, “fmode:ext_enc”, or “fmode:ext_enc:int_enc”.

    See the documentation of IO.new for full documentation of the mode string directives.

    If a file is being created, its initial permissions may be set using the perm parameter. See File.new and the open(2) and chmod(2) man pages for a description of permissions.

    If a block is specified, it will be invoked with the IO object as a parameter, and the IO will be automatically closed when the block terminates. The call returns the value of the block.

    If path starts with a pipe character ("|"), a subprocess is created, connected to the caller by a pair of pipes. The returned IO object may be used to write to the standard input and read from the standard output of this subprocess.

    If the command following the pipe is a single minus sign ("|-"), Ruby forks, and this subprocess is connected to the parent. If the command is not "-", the subprocess runs the command.

    When the subprocess is Ruby (opened via "|-"), the open call returns nil. If a block is associated with the open call, that block will run twice — once in the parent and once in the child.

    The block parameter will be an IO object in the parent and nil in the child. The parent’s IO object will be connected to the child’s $stdin and $stdout. The subprocess will be terminated at the end of the block.

    Examples

    Reading from “testfile”:

    open("testfile") do |f|
      print f.gets
    end
    

    Produces:

    This is line one
    

    Open a subprocess and read its output:

    cmd = open("|date")
    print cmd.gets
    cmd.close
    

    Produces:

    Wed Apr  9 08:56:31 CDT 2003

    Open a subprocess running the same Ruby program:

    f = open("|-", "w+")
    if f.nil?
      puts "in Child"
      exit
    else
      puts "Got: #{f.gets}"
    end
    

    Produces:

    Got: in Child

    Open a subprocess using a block to receive the IO object:

    open "|-" do |f|
      if f then
        # parent process
        puts "Got: #{f.gets}"
      else
        # child process
        puts "in Child"
      end
    end
    

    Produces:

    Got: in Child
     
                   static VALUE
    rb_f_open(int argc, VALUE *argv)
    {
        ID to_open = 0;
        int redirect = FALSE;
    
        if (argc >= 1) {
            CONST_ID(to_open, "to_open");
            if (rb_respond_to(argv[0], to_open)) {
                redirect = TRUE;
            }
            else {
                VALUE tmp = argv[0];
                FilePathValue(tmp);
                if (NIL_P(tmp)) {
                    redirect = TRUE;
                }
                else {
                    VALUE cmd = check_pipe_command(tmp);
                    if (!NIL_P(cmd)) {
                        argv[0] = cmd;
                        return rb_io_s_popen(argc, argv, rb_cIO);
                    }
                }
            }
        }
        if (redirect) {
            VALUE io = rb_funcall2(argv[0], to_open, argc-1, argv+1);
    
            if (rb_block_given_p()) {
                return rb_ensure(rb_yield, io, io_close, io);
            }
            return io;
        }
        return rb_io_s_open(argc, argv, rb_cFile);
    }
                
    p(obj) → obj click to toggle source
    p(obj1, obj2, ...) → [obj, ...]
    p() → nil

    For each object, directly writes obj.inspect followed by a newline to the program’s standard output.

    S = Struct.new(:name, :state)
    s = S['dave', 'TX']
    p s
    

    produces:

    #<S name="dave", state="TX">
    
     
                   static VALUE
    rb_f_p(int argc, VALUE *argv, VALUE self)
    {
        struct rb_f_p_arg arg;
        arg.argc = argc;
        arg.argv = argv;
    
        return rb_uninterruptible(rb_f_p_internal, (VALUE)&arg);
    }
                
    printf(io, string [, obj ... ]) → nil click to toggle source
    printf(string [, obj ... ]) → nil

    Equivalent to:

    io.write(sprintf(string, obj, ...))

    or

    $stdout.write(sprintf(string, obj, ...))
     
                   static VALUE
    rb_f_printf(int argc, VALUE *argv)
    {
        VALUE out;
    
        if (argc == 0) return Qnil;
        if (RB_TYPE_P(argv[0], T_STRING)) {
            out = rb_stdout;
        }
        else {
            out = argv[0];
            argv++;
            argc--;
        }
        rb_io_write(out, rb_f_sprintf(argc, argv));
    
        return Qnil;
    }
                
    proc { |...| block } → a_proc click to toggle source

    Equivalent to Proc.new.

     
                   VALUE
    rb_block_proc(void)
    {
        return proc_new(rb_cProc, FALSE);
    }
                
    putc(int) → int click to toggle source

    Equivalent to:

    $stdout.putc(int)
    

    Refer to the documentation for IO#putc for important information regarding multi-byte characters.

     
                   static VALUE
    rb_f_putc(VALUE recv, VALUE ch)
    {
        if (recv == rb_stdout) {
            return rb_io_putc(recv, ch);
        }
        return rb_funcall2(rb_stdout, rb_intern("putc"), 1, &ch);
    }
                
    puts(obj, ...) → nil click to toggle source

    Equivalent to

    $stdout.puts(obj, ...)
     
                   static VALUE
    rb_f_puts(int argc, VALUE *argv, VALUE recv)
    {
        if (recv == rb_stdout) {
            return rb_io_puts(argc, argv, recv);
        }
        return rb_funcall2(rb_stdout, rb_intern("puts"), argc, argv);
    }
                
    raise click to toggle source
    raise(string)
    raise(exception [, string [, array]])

    With no arguments, raises the exception in $! or raises a RuntimeError if $! is nil. With a single String argument, raises a RuntimeError with the string as a message. Otherwise, the first parameter should be the name of an Exception class (or an object that returns an Exception object when sent an exception message). The optional second parameter sets the message associated with the exception, and the third parameter is an array of callback information. Exceptions are caught by the rescue clause of begin...end blocks.

    raise "Failed to create socket"
    raise ArgumentError, "No parameters", caller
    
     
                   static VALUE
    rb_f_raise(int argc, VALUE *argv)
    {
        VALUE err;
        VALUE opts[raise_max_opt], *const cause = &opts[raise_opt_cause];
    
        argc = extract_raise_opts(argc, argv, opts);
        if (argc == 0) {
            if (*cause != Qundef) {
                rb_raise(rb_eArgError, "only cause is given with no arguments");
            }
            err = get_errinfo();
            if (!NIL_P(err)) {
                argc = 1;
                argv = &err;
            }
        }
        rb_raise_jump(rb_make_exception(argc, argv), *cause);
    
        UNREACHABLE;
    }
                
    rand(max=0) → number click to toggle source

    If called without an argument, or if max.to_i.abs == 0, rand returns a pseudo-random floating point number between 0.0 and 1.0, including 0.0 and excluding 1.0.

    rand        #=> 0.2725926052826416
    

    When max.abs is greater than or equal to 1, rand returns a pseudo-random integer greater than or equal to 0 and less than max.to_i.abs.

    rand(100)   #=> 12
    

    When max is a Range, rand returns a random number where range.member?(number) == true.

    Negative or floating point values for max are allowed, but may give surprising results.

    rand(-100) # => 87
    rand(-0.5) # => 0.8130921818028143
    rand(1.9)  # equivalent to rand(1), which is always 0
    

    #srand may be used to ensure that sequences of random numbers are reproducible between different runs of a program.

    See also Random#rand.

     
                   static VALUE
    rb_f_rand(int argc, VALUE *argv, VALUE obj)
    {
        VALUE v, vmax, r;
        rb_random_t *rnd = rand_start(&default_rand);
    
        if (argc == 0) goto zero_arg;
        rb_scan_args(argc, argv, "01", &vmax);
        if (NIL_P(vmax)) goto zero_arg;
        if ((v = rand_range(Qnil, rnd, vmax)) != Qfalse) {
            return v;
        }
        vmax = rb_to_int(vmax);
        if (vmax == INT2FIX(0) || NIL_P(r = rand_int(Qnil, rnd, vmax, 0))) {
          zero_arg:
            return DBL2NUM(genrand_real(&rnd->mt));
        }
        return r;
    }
                
    readline(sep=$/) → string click to toggle source
    readline(limit) → string
    readline(sep, limit) → string

    Equivalent to Kernel::gets, except readline raises EOFError at end of file.

     
                   static VALUE
    rb_f_readline(int argc, VALUE *argv, VALUE recv)
    {
        if (recv == argf) {
            return argf_readline(argc, argv, argf);
        }
        return rb_funcall2(argf, rb_intern("readline"), argc, argv);
    }
                
    readlines(sep=$/) → array click to toggle source
    readlines(limit) → array
    readlines(sep, limit) → array

    Returns an array containing the lines returned by calling Kernel.gets(sep) until the end of file.

     
                   static VALUE
    rb_f_readlines(int argc, VALUE *argv, VALUE recv)
    {
        if (recv == argf) {
            return argf_readlines(argc, argv, argf);
        }
        return rb_funcall2(argf, rb_intern("readlines"), argc, argv);
    }
                
    require(name) → true or false click to toggle source

    Loads the given name, returning true if successful and false if the feature is already loaded.

    If the filename does not resolve to an absolute path, it will be searched for in the directories listed in $LOAD_PATH ($:).

    If the filename has the extension “.rb”, it is loaded as a source file; if the extension is “.so”, “.o”, or “.dll”, or the default shared library extension on the current platform, Ruby loads the shared library as a Ruby extension. Otherwise, Ruby tries adding “.rb”, “.so”, and so on to the name until found. If the file named cannot be found, a LoadError will be raised.

    For Ruby extensions the filename given may use any shared library extension. For example, on Linux the socket extension is “socket.so” and require 'socket.dll' will load the socket extension.

    The absolute path of the loaded file is added to $LOADED_FEATURES ($"). A file will not be loaded again if its path already appears in $". For example, require 'a'; require './a' will not load a.rb again.

    require "my-library.rb"
    require "db-driver"
    

    Any constants or globals within the loaded source file will be available in the calling program’s global namespace. However, local variables will not be propagated to the loading environment.

     
                   VALUE
    rb_f_require(VALUE obj, VALUE fname)
    {
        return rb_require_safe(fname, rb_safe_level());
    }
                
    require_relative(string) → true or false click to toggle source

    Ruby tries to load the library named string relative to the requiring file’s path. If the file’s path cannot be determined a LoadError is raised. If a file is loaded true is returned and false otherwise.

     
                   VALUE
    rb_f_require_relative(VALUE obj, VALUE fname)
    {
        VALUE base = rb_current_realfilepath();
        if (NIL_P(base)) {
            rb_loaderror("cannot infer basepath");
        }
        base = rb_file_dirname(base);
        return rb_require_safe(rb_file_absolute_path(fname, base), rb_safe_level());
    }
                
    select(read_array [, write_array [, error_array [, timeout]]]) → array or nil click to toggle source

    Calls select(2) system call. It monitors given arrays of IO objects, waits until one or more of IO objects are ready for reading, are ready for writing, and have pending exceptions respectively, and returns an array that contains arrays of those IO objects. It will return nil if optional timeout value is given and no IO object is ready in timeout seconds.

    IO.select peeks the buffer of IO objects for testing readability. If the IO buffer is not empty, IO.select immediately notifies readability. This "peek" only happens for IO objects. It does not happen for IO-like objects such as OpenSSL::SSL::SSLSocket.

    The best way to use IO.select is invoking it after nonblocking methods such as read_nonblock, write_nonblock, etc. The methods raise an exception which is extended by IO::WaitReadable or IO::WaitWritable. The modules notify how the caller should wait with IO.select. If IO::WaitReadable is raised, the caller should wait for reading. If IO::WaitWritable is raised, the caller should wait for writing.

    So, blocking read (readpartial) can be emulated using read_nonblock and IO.select as follows:

    begin
      result = io_like.read_nonblock(maxlen)
    rescue IO::WaitReadable
      IO.select([io_like])
      retry
    rescue IO::WaitWritable
      IO.select(nil, [io_like])
      retry
    end
    

    Especially, the combination of nonblocking methods and IO.select is preferred for IO like objects such as OpenSSL::SSL::SSLSocket. It has to_io method to return underlying IO object. IO.select calls to_io to obtain the file descriptor to wait.

    This means that readability notified by IO.select doesn’t mean readability from OpenSSL::SSL::SSLSocket object.

    The most likely situation is that OpenSSL::SSL::SSLSocket buffers some data. IO.select doesn’t see the buffer. So IO.select can block when OpenSSL::SSL::SSLSocket#readpartial doesn’t block.

    However, several more complicated situations exist.

    SSL is a protocol which is sequence of records. The record consists of multiple bytes. So, the remote side of SSL sends a partial record, IO.select notifies readability but OpenSSL::SSL::SSLSocket cannot decrypt a byte and OpenSSL::SSL::SSLSocket#readpartial will blocks.

    Also, the remote side can request SSL renegotiation which forces the local SSL engine to write some data. This means OpenSSL::SSL::SSLSocket#readpartial may invoke write system call and it can block. In such a situation, OpenSSL::SSL::SSLSocket#read_nonblock raises IO::WaitWritable instead of blocking. So, the caller should wait for ready for writability as above example.

    The combination of nonblocking methods and IO.select is also useful for streams such as tty, pipe socket socket when multiple processes read from a stream.

    Finally, Linux kernel developers don’t guarantee that readability of select(2) means readability of following read(2) even for a single process. See select(2) manual on GNU/Linux system.

    Invoking IO.select before IO#readpartial works well as usual. However it is not the best way to use IO.select.

    The writability notified by select(2) doesn’t show how many bytes writable. IO#write method blocks until given whole string is written. So, IO#write(two or more bytes) can block after writability is notified by IO.select. IO#write_nonblock is required to avoid the blocking.

    Blocking write (write) can be emulated using write_nonblock and IO.select as follows: IO::WaitReadable should also be rescued for SSL renegotiation in OpenSSL::SSL::SSLSocket.

    while 0 < string.bytesize
      begin
        written = io_like.write_nonblock(string)
      rescue IO::WaitReadable
        IO.select([io_like])
        retry
      rescue IO::WaitWritable
        IO.select(nil, [io_like])
        retry
      end
      string = string.byteslice(written..-1)
    end
    

    Parameters

    read_array

    an array of IO objects that wait until ready for read

    write_array

    an array of IO objects that wait until ready for write

    error_array

    an array of IO objects that wait for exceptions

    timeout

    a numeric value in second

    Example

    rp, wp = IO.pipe
    mesg = "ping "
    100.times {
      # IO.select follows IO#read.  Not the best way to use IO.select.
      rs, ws, = IO.select([rp], [wp])
      if r = rs[0]
        ret = r.read(5)
        print ret
        case ret
        when /ping/
          mesg = "pong\n"
        when /pong/
          mesg = "ping "
        end
      end
      if w = ws[0]
        w.write(mesg)
      end
    }
    

    produces:

    ping pong
    ping pong
    ping pong
    (snipped)
    ping
    
     
                   static VALUE
    rb_f_select(int argc, VALUE *argv, VALUE obj)
    {
        VALUE timeout;
        struct select_args args;
        struct timeval timerec;
        int i;
    
        rb_scan_args(argc, argv, "13", &args.read, &args.write, &args.except, &timeout);
        if (NIL_P(timeout)) {
            args.timeout = 0;
        }
        else {
            timerec = rb_time_interval(timeout);
            args.timeout = &timerec;
        }
    
        for (i = 0; i < numberof(args.fdsets); ++i)
            rb_fd_init(&args.fdsets[i]);
    
        return rb_ensure(select_call, (VALUE)&args, select_end, (VALUE)&args);
    }
                
    set_trace_func(proc) → proc click to toggle source
    set_trace_func(nil) → nil

    Establishes proc as the handler for tracing, or disables tracing if the parameter is nil.

    Note: this method is obsolete, please use TracePoint instead.

    proc takes up to six parameters:

    • an event name

    • a filename

    • a line number

    • an object id

    • a binding

    • the name of a class

    proc is invoked whenever an event occurs.

    Events are:

    c-call

    call a C-language routine

    c-return

    return from a C-language routine

    call

    call a Ruby method

    class

    start a class or module definition),

    end

    finish a class or module definition),

    line

    execute code on a new line

    raise

    raise an exception

    return

    return from a Ruby method

    Tracing is disabled within the context of proc.

      class Test
      def test
        a = 1
        b = 2
      end
      end
    
      set_trace_func proc { |event, file, line, id, binding, classname|
         printf "%8s %s:%-2d %10s %8s\n", event, file, line, id, classname
      }
      t = Test.new
      t.test
    
        line prog.rb:11               false
      c-call prog.rb:11        new    Class
      c-call prog.rb:11 initialize   Object
    c-return prog.rb:11 initialize   Object
    c-return prog.rb:11        new    Class
        line prog.rb:12               false
        call prog.rb:2        test     Test
        line prog.rb:3        test     Test
        line prog.rb:4        test     Test
      return prog.rb:4        test     Test
     
                   static VALUE
    set_trace_func(VALUE obj, VALUE trace)
    {
    
        rb_remove_event_hook(call_trace_func);
    
        if (NIL_P(trace)) {
            return Qnil;
        }
    
        if (!rb_obj_is_proc(trace)) {
            rb_raise(rb_eTypeError, "trace_func needs to be Proc");
        }
    
        rb_add_event_hook(call_trace_func, RUBY_EVENT_ALL, trace);
        return trace;
    }
                
    sleep([duration]) → fixnum click to toggle source

    Suspends the current thread for duration seconds (which may be any number, including a Float with fractional seconds). Returns the actual number of seconds slept (rounded), which may be less than that asked for if another thread calls Thread#run. Called without an argument, sleep() will sleep forever.

    Time.new    #=> 2008-03-08 19:56:19 +0900
    sleep 1.2   #=> 1
    Time.new    #=> 2008-03-08 19:56:20 +0900
    sleep 1.9   #=> 2
    Time.new    #=> 2008-03-08 19:56:22 +0900
    
     
                   static VALUE
    rb_f_sleep(int argc, VALUE *argv)
    {
        time_t beg, end;
    
        beg = time(0);
        if (argc == 0) {
            rb_thread_sleep_forever();
        }
        else {
            rb_check_arity(argc, 0, 1);
            rb_thread_wait_for(rb_time_interval(argv[0]));
        }
    
        end = time(0) - beg;
    
        return INT2FIX(end);
    }
                
    spawn([env,] command... [,options]) → pid click to toggle source
    spawn([env,] command... [,options]) → pid

    spawn executes specified command and return its pid.

    pid = spawn("tar xf ruby-2.0.0-p195.tar.bz2")
    Process.wait pid
    
    pid = spawn(RbConfig.ruby, "-eputs'Hello, world!'")
    Process.wait pid
    

    This method is similar to #system but it doesn’t wait for the command to finish.

    The parent process should use Process.wait to collect the termination status of its child or use Process.detach to register disinterest in their status; otherwise, the operating system may accumulate zombie processes.

    spawn has bunch of options to specify process attributes:

    env: hash
      name => val : set the environment variable
      name => nil : unset the environment variable
    
      the keys and the values except for +nil+ must be strings.
    command...:
      commandline                 : command line string which is passed to the standard shell
      cmdname, arg1, ...          : command name and one or more arguments (This form does not use the shell. See below for caveats.)
      [cmdname, argv0], arg1, ... : command name, argv[0] and zero or more arguments (no shell)
    options: hash
      clearing environment variables:
        :unsetenv_others => true   : clear environment variables except specified by env
        :unsetenv_others => false  : don't clear (default)
      process group:
        :pgroup => true or 0 : make a new process group
        :pgroup => pgid      : join the specified process group
        :pgroup => nil       : don't change the process group (default)
      create new process group: Windows only
        :new_pgroup => true  : the new process is the root process of a new process group
        :new_pgroup => false : don't create a new process group (default)
      resource limit: resourcename is core, cpu, data, etc.  See Process.setrlimit.
        :rlimit_resourcename => limit
        :rlimit_resourcename => [cur_limit, max_limit]
      umask:
        :umask => int
      redirection:
        key:
          FD              : single file descriptor in child process
          [FD, FD, ...]   : multiple file descriptor in child process
        value:
          FD                        : redirect to the file descriptor in parent process
          string                    : redirect to file with open(string, "r" or "w")
          [string]                  : redirect to file with open(string, File::RDONLY)
          [string, open_mode]       : redirect to file with open(string, open_mode, 0644)
          [string, open_mode, perm] : redirect to file with open(string, open_mode, perm)
          [:child, FD]              : redirect to the redirected file descriptor
          :close                    : close the file descriptor in child process
        FD is one of follows
          :in     : the file descriptor 0 which is the standard input
          :out    : the file descriptor 1 which is the standard output
          :err    : the file descriptor 2 which is the standard error
          integer : the file descriptor of specified the integer
          io      : the file descriptor specified as io.fileno
      file descriptor inheritance: close non-redirected non-standard fds (3, 4, 5, ...) or not
        :close_others => true  : don't inherit
      current directory:
        :chdir => str
    
      The 'cmdname, arg1, ...' form does not use the shell. However,
      on different OSes, different things are provided as built-in
      commands. An example of this is 'echo', which is a built-in
      on Windows, but is a normal program on Linux and Mac OS X.
      This means that `Process.spawn 'echo', '%Path%'` will display
      the contents of the `%Path%` environment variable on Windows,
      but `Process.spawn 'echo', '$PATH'` prints the literal '$PATH'.

    If a hash is given as env, the environment is updated by env before exec(2) in the child process. If a pair in env has nil as the value, the variable is deleted.

    # set FOO as BAR and unset BAZ.
    pid = spawn({"FOO"=>"BAR", "BAZ"=>nil}, command)
    

    If a hash is given as options, it specifies process group, create new process group, resource limit, current directory, umask and redirects for the child process. Also, it can be specified to clear environment variables.

    The :unsetenv_others key in options specifies to clear environment variables, other than specified by env.

    pid = spawn(command, :unsetenv_others=>true) # no environment variable
    pid = spawn({"FOO"=>"BAR"}, command, :unsetenv_others=>true) # FOO only
    

    The :pgroup key in options specifies a process group. The corresponding value should be true, zero, a positive integer, or nil. true and zero cause the process to be a process leader of a new process group. A non-zero positive integer causes the process to join the provided process group. The default value, nil, causes the process to remain in the same process group.

    pid = spawn(command, :pgroup=>true) # process leader
    pid = spawn(command, :pgroup=>10) # belongs to the process group 10
    

    The :new_pgroup key in options specifies to pass CREATE_NEW_PROCESS_GROUP flag to CreateProcessW() that is Windows API. This option is only for Windows. true means the new process is the root process of the new process group. The new process has CTRL+C disabled. This flag is necessary for Process.kill(:SIGINT, pid) on the subprocess. :new_pgroup is false by default.

    pid = spawn(command, :new_pgroup=>true)  # new process group
    pid = spawn(command, :new_pgroup=>false) # same process group
    

    The :rlimit_foo key specifies a resource limit. foo should be one of resource types such as core. The corresponding value should be an integer or an array which have one or two integers: same as cur_limit and max_limit arguments for Process.setrlimit.

    cur, max = Process.getrlimit(:CORE)
    pid = spawn(command, :rlimit_core=>[0,max]) # disable core temporary.
    pid = spawn(command, :rlimit_core=>max) # enable core dump
    pid = spawn(command, :rlimit_core=>0) # never dump core.
    

    The :umask key in options specifies the umask.

    pid = spawn(command, :umask=>077)
    

    The :in, :out, :err, a fixnum, an IO and an array key specifies a redirection. The redirection maps a file descriptor in the child process.

    For example, stderr can be merged into stdout as follows:

    pid = spawn(command, :err=>:out)
    pid = spawn(command, 2=>1)
    pid = spawn(command, STDERR=>:out)
    pid = spawn(command, STDERR=>STDOUT)
    

    The hash keys specifies a file descriptor in the child process started by spawn. :err, 2 and STDERR specifies the standard error stream (stderr).

    The hash values specifies a file descriptor in the parent process which invokes spawn. :out, 1 and STDOUT specifies the standard output stream (stdout).

    In the above example, the standard output in the child process is not specified. So it is inherited from the parent process.

    The standard input stream (stdin) can be specified by :in, 0 and STDIN.

    A filename can be specified as a hash value.

    pid = spawn(command, :in=>"/dev/null") # read mode
    pid = spawn(command, :out=>"/dev/null") # write mode
    pid = spawn(command, :err=>"log") # write mode
    pid = spawn(command, [:out, :err]=>"/dev/null") # write mode
    pid = spawn(command, 3=>"/dev/null") # read mode
    

    For stdout and stderr (and combination of them), it is opened in write mode. Otherwise read mode is used.

    For specifying flags and permission of file creation explicitly, an array is used instead.

    pid = spawn(command, :in=>["file"]) # read mode is assumed
    pid = spawn(command, :in=>["file", "r"])
    pid = spawn(command, :out=>["log", "w"]) # 0644 assumed
    pid = spawn(command, :out=>["log", "w", 0600])
    pid = spawn(command, :out=>["log", File::WRONLY|File::EXCL|File::CREAT, 0600])
    

    The array specifies a filename, flags and permission. The flags can be a string or an integer. If the flags is omitted or nil, File::RDONLY is assumed. The permission should be an integer. If the permission is omitted or nil, 0644 is assumed.

    If an array of IOs and integers are specified as a hash key, all the elements are redirected.

    # stdout and stderr is redirected to log file.
    # The file "log" is opened just once.
    pid = spawn(command, [:out, :err]=>["log", "w"])
    

    Another way to merge multiple file descriptors is [:child, fd]. [:child, fd] means the file descriptor in the child process. This is different from fd. For example, :err=>:out means redirecting child stderr to parent stdout. But :err=>[:child, :out] means redirecting child stderr to child stdout. They differ if stdout is redirected in the child process as follows.

    # stdout and stderr is redirected to log file.
    # The file "log" is opened just once.
    pid = spawn(command, :out=>["log", "w"], :err=>[:child, :out])
    

    [:child, :out] can be used to merge stderr into stdout in IO.popen. In this case, IO.popen redirects stdout to a pipe in the child process and [:child, :out] refers the redirected stdout.

    io = IO.popen(["sh", "-c", "echo out; echo err >&2", :err=>[:child, :out]])
    p io.read #=> "out\nerr\n"
    

    The :chdir key in options specifies the current directory.

    pid = spawn(command, :chdir=>"/var/tmp")
    

    spawn closes all non-standard unspecified descriptors by default. The “standard” descriptors are 0, 1 and 2. This behavior is specified by :close_others option. :close_others doesn’t affect the standard descriptors which are closed only if :close is specified explicitly.

    pid = spawn(command, :close_others=>true)  # close 3,4,5,... (default)
    pid = spawn(command, :close_others=>false) # don't close 3,4,5,...
    

    :close_others is true by default for spawn and IO.popen.

    Note that fds which close-on-exec flag is already set are closed regardless of :close_others option.

    So IO.pipe and spawn can be used as IO.popen.

    # similar to r = IO.popen(command)
    r, w = IO.pipe
    pid = spawn(command, :out=>w)   # r, w is closed in the child process.
    w.close
    

    :close is specified as a hash value to close a fd individually.

    f = open(foo)
    system(command, f=>:close)        # don't inherit f.
    

    If a file descriptor need to be inherited, io=>io can be used.

    # valgrind has --log-fd option for log destination.
    # log_w=>log_w indicates log_w.fileno inherits to child process.
    log_r, log_w = IO.pipe
    pid = spawn("valgrind", "--log-fd=#{log_w.fileno}", "echo", "a", log_w=>log_w)
    log_w.close
    p log_r.read
    

    It is also possible to exchange file descriptors.

    pid = spawn(command, :out=>:err, :err=>:out)
    

    The hash keys specify file descriptors in the child process. The hash values specifies file descriptors in the parent process. So the above specifies exchanging stdout and stderr. Internally, spawn uses an extra file descriptor to resolve such cyclic file descriptor mapping.

    See Kernel.exec for the standard shell.

     
                   static VALUE
    rb_f_spawn(int argc, VALUE *argv)
    {
        rb_pid_t pid;
        char errmsg[CHILD_ERRMSG_BUFLEN] = { '\0' };
        VALUE execarg_obj, fail_str;
        struct rb_execarg *eargp;
    
        execarg_obj = rb_execarg_new(argc, argv, TRUE);
        eargp = rb_execarg_get(execarg_obj);
        fail_str = eargp->use_shell ? eargp->invoke.sh.shell_script : eargp->invoke.cmd.command_name;
    
        pid = rb_execarg_spawn(execarg_obj, errmsg, sizeof(errmsg));
    
        if (pid == -1) {
            int err = errno;
            rb_exec_fail(eargp, err, errmsg);
            RB_GC_GUARD(execarg_obj);
            rb_syserr_fail_str(err, fail_str);
        }
    #if defined(HAVE_WORKING_FORK) || defined(HAVE_SPAWNV)
        return PIDT2NUM(pid);
    #else
        return Qnil;
    #endif
    }
                
    sprintf(format_string [, arguments...] ) → string click to toggle source

    Returns the string resulting from applying format_string to any additional arguments. Within the format string, any characters other than format sequences are copied to the result.

    The syntax of a format sequence is follows.

    %[flags][width][.precision]type

    A format sequence consists of a percent sign, followed by optional flags, width, and precision indicators, then terminated with a field type character. The field type controls how the corresponding sprintf argument is to be interpreted, while the flags modify that interpretation.

    The field type characters are:

    Field |  Integer Format
    ------+--------------------------------------------------------------
      b   | Convert argument as a binary number.
          | Negative numbers will be displayed as a two's complement
          | prefixed with `..1'.
      B   | Equivalent to `b', but uses an uppercase 0B for prefix
          | in the alternative format by #.
      d   | Convert argument as a decimal number.
      i   | Identical to `d'.
      o   | Convert argument as an octal number.
          | Negative numbers will be displayed as a two's complement
          | prefixed with `..7'.
      u   | Identical to `d'.
      x   | Convert argument as a hexadecimal number.
          | Negative numbers will be displayed as a two's complement
          | prefixed with `..f' (representing an infinite string of
          | leading 'ff's).
      X   | Equivalent to `x', but uses uppercase letters.
    
    Field |  Float Format
    ------+--------------------------------------------------------------
      e   | Convert floating point argument into exponential notation
          | with one digit before the decimal point as [-]d.dddddde[+-]dd.
          | The precision specifies the number of digits after the decimal
          | point (defaulting to six).
      E   | Equivalent to `e', but uses an uppercase E to indicate
          | the exponent.
      f   | Convert floating point argument as [-]ddd.dddddd,
          | where the precision specifies the number of digits after
          | the decimal point.
      g   | Convert a floating point number using exponential form
          | if the exponent is less than -4 or greater than or
          | equal to the precision, or in dd.dddd form otherwise.
          | The precision specifies the number of significant digits.
      G   | Equivalent to `g', but use an uppercase `E' in exponent form.
      a   | Convert floating point argument as [-]0xh.hhhhp[+-]dd,
          | which is consisted from optional sign, "0x", fraction part
          | as hexadecimal, "p", and exponential part as decimal.
      A   | Equivalent to `a', but use uppercase `X' and `P'.
    
    Field |  Other Format
    ------+--------------------------------------------------------------
      c   | Argument is the numeric code for a single character or
          | a single character string itself.
      p   | The valuing of argument.inspect.
      s   | Argument is a string to be substituted.  If the format
          | sequence contains a precision, at most that many characters
          | will be copied.
      %   | A percent sign itself will be displayed.  No argument taken.

    The flags modifies the behavior of the formats. The flag characters are:

    Flag     | Applies to    | Meaning
    ---------+---------------+-----------------------------------------
    space    | bBdiouxX      | Leave a space at the start of
             | aAeEfgG       | non-negative numbers.
             | (numeric fmt) | For `o', `x', `X', `b' and `B', use
             |               | a minus sign with absolute value for
             |               | negative values.
    ---------+---------------+-----------------------------------------
    (digit)$ | all           | Specifies the absolute argument number
             |               | for this field.  Absolute and relative
             |               | argument numbers cannot be mixed in a
             |               | sprintf string.
    ---------+---------------+-----------------------------------------
     #       | bBoxX         | Use an alternative format.
             | aAeEfgG       | For the conversions `o', increase the precision
             |               | until the first digit will be `0' if
             |               | it is not formatted as complements.
             |               | For the conversions `x', `X', `b' and `B'
             |               | on non-zero, prefix the result with ``0x'',
             |               | ``0X'', ``0b'' and ``0B'', respectively.
             |               | For `a', `A', `e', `E', `f', `g', and 'G',
             |               | force a decimal point to be added,
             |               | even if no digits follow.
             |               | For `g' and 'G', do not remove trailing zeros.
    ---------+---------------+-----------------------------------------
    +        | bBdiouxX      | Add a leading plus sign to non-negative
             | aAeEfgG       | numbers.
             | (numeric fmt) | For `o', `x', `X', `b' and `B', use
             |               | a minus sign with absolute value for
             |               | negative values.
    ---------+---------------+-----------------------------------------
    -        | all           | Left-justify the result of this conversion.
    ---------+---------------+-----------------------------------------
    0 (zero) | bBdiouxX      | Pad with zeros, not spaces.
             | aAeEfgG       | For `o', `x', `X', `b' and `B', radix-1
             | (numeric fmt) | is used for negative numbers formatted as
             |               | complements.
    ---------+---------------+-----------------------------------------
    *        | all           | Use the next argument as the field width.
             |               | If negative, left-justify the result. If the
             |               | asterisk is followed by a number and a dollar
             |               | sign, use the indicated argument as the width.

    Examples of flags:

    # `+' and space flag specifies the sign of non-negative numbers.
    sprintf("%d", 123)  #=> "123"
    sprintf("%+d", 123) #=> "+123"
    sprintf("% d", 123) #=> " 123"
    
    # `#' flag for `o' increases number of digits to show `0'.
    # `+' and space flag changes format of negative numbers.
    sprintf("%o", 123)   #=> "173"
    sprintf("%#o", 123)  #=> "0173"
    sprintf("%+o", -123) #=> "-173"
    sprintf("%o", -123)  #=> "..7605"
    sprintf("%#o", -123) #=> "..7605"
    
    # `#' flag for `x' add a prefix `0x' for non-zero numbers.
    # `+' and space flag disables complements for negative numbers.
    sprintf("%x", 123)   #=> "7b"
    sprintf("%#x", 123)  #=> "0x7b"
    sprintf("%+x", -123) #=> "-7b"
    sprintf("%x", -123)  #=> "..f85"
    sprintf("%#x", -123) #=> "0x..f85"
    sprintf("%#x", 0)    #=> "0"
    
    # `#' for `X' uses the prefix `0X'.
    sprintf("%X", 123)  #=> "7B"
    sprintf("%#X", 123) #=> "0X7B"
    
    # `#' flag for `b' add a prefix `0b' for non-zero numbers.
    # `+' and space flag disables complements for negative numbers.
    sprintf("%b", 123)   #=> "1111011"
    sprintf("%#b", 123)  #=> "0b1111011"
    sprintf("%+b", -123) #=> "-1111011"
    sprintf("%b", -123)  #=> "..10000101"
    sprintf("%#b", -123) #=> "0b..10000101"
    sprintf("%#b", 0)    #=> "0"
    
    # `#' for `B' uses the prefix `0B'.
    sprintf("%B", 123)  #=> "1111011"
    sprintf("%#B", 123) #=> "0B1111011"
    
    # `#' for `e' forces to show the decimal point.
    sprintf("%.0e", 1)  #=> "1e+00"
    sprintf("%#.0e", 1) #=> "1.e+00"
    
    # `#' for `f' forces to show the decimal point.
    sprintf("%.0f", 1234)  #=> "1234"
    sprintf("%#.0f", 1234) #=> "1234."
    
    # `#' for `g' forces to show the decimal point.
    # It also disables stripping lowest zeros.
    sprintf("%g", 123.4)   #=> "123.4"
    sprintf("%#g", 123.4)  #=> "123.400"
    sprintf("%g", 123456)  #=> "123456"
    sprintf("%#g", 123456) #=> "123456."
    

    The field width is an optional integer, followed optionally by a period and a precision. The width specifies the minimum number of characters that will be written to the result for this field.

    Examples of width:

    # padding is done by spaces,       width=20
    # 0 or radix-1.             <------------------>
    sprintf("%20d", 123)   #=> "                 123"
    sprintf("%+20d", 123)  #=> "                +123"
    sprintf("%020d", 123)  #=> "00000000000000000123"
    sprintf("%+020d", 123) #=> "+0000000000000000123"
    sprintf("% 020d", 123) #=> " 0000000000000000123"
    sprintf("%-20d", 123)  #=> "123                 "
    sprintf("%-+20d", 123) #=> "+123                "
    sprintf("%- 20d", 123) #=> " 123                "
    sprintf("%020x", -123) #=> "..ffffffffffffffff85"
    

    For numeric fields, the precision controls the number of decimal places displayed. For string fields, the precision determines the maximum number of characters to be copied from the string. (Thus, the format sequence %10.10s will always contribute exactly ten characters to the result.)

    Examples of precisions:

    # precision for `d', 'o', 'x' and 'b' is
    # minimum number of digits               <------>
    sprintf("%20.8d", 123)  #=> "            00000123"
    sprintf("%20.8o", 123)  #=> "            00000173"
    sprintf("%20.8x", 123)  #=> "            0000007b"
    sprintf("%20.8b", 123)  #=> "            01111011"
    sprintf("%20.8d", -123) #=> "           -00000123"
    sprintf("%20.8o", -123) #=> "            ..777605"
    sprintf("%20.8x", -123) #=> "            ..ffff85"
    sprintf("%20.8b", -11)  #=> "            ..110101"
    
    # "0x" and "0b" for `#x' and `#b' is not counted for
    # precision but "0" for `#o' is counted.  <------>
    sprintf("%#20.8d", 123)  #=> "            00000123"
    sprintf("%#20.8o", 123)  #=> "            00000173"
    sprintf("%#20.8x", 123)  #=> "          0x0000007b"
    sprintf("%#20.8b", 123)  #=> "          0b01111011"
    sprintf("%#20.8d", -123) #=> "           -00000123"
    sprintf("%#20.8o", -123) #=> "            ..777605"
    sprintf("%#20.8x", -123) #=> "          0x..ffff85"
    sprintf("%#20.8b", -11)  #=> "          0b..110101"
    
    # precision for `e' is number of
    # digits after the decimal point           <------>
    sprintf("%20.8e", 1234.56789) #=> "      1.23456789e+03"
    
    # precision for `f' is number of
    # digits after the decimal point               <------>
    sprintf("%20.8f", 1234.56789) #=> "       1234.56789000"
    
    # precision for `g' is number of
    # significant digits                          <------->
    sprintf("%20.8g", 1234.56789) #=> "           1234.5679"
    
    #                                         <------->
    sprintf("%20.8g", 123456789)  #=> "       1.2345679e+08"
    
    # precision for `s' is
    # maximum number of characters                    <------>
    sprintf("%20.8s", "string test") #=> "            string t"
    

    Examples:

    sprintf("%d %04x", 123, 123)               #=> "123 007b"
    sprintf("%08b '%4s'", 123, 123)            #=> "01111011 ' 123'"
    sprintf("%1$*2$s %2$d %1$s", "hello", 8)   #=> "   hello 8 hello"
    sprintf("%1$*2$s %2$d", "hello", -8)       #=> "hello    -8"
    sprintf("%+g:% g:%-g", 1.23, 1.23, 1.23)   #=> "+1.23: 1.23:1.23"
    sprintf("%u", -123)                        #=> "-123"
    

    For more complex formatting, Ruby supports a reference by name. %<name>s style uses format style, but %{name} style doesn't.

    Examples:

    sprintf("%<foo>d : %<bar>f", { :foo => 1, :bar => 2 })
      #=> 1 : 2.000000
    sprintf("%{foo}f", { :foo => 1 })
      # => "1f"
    
     
                   VALUE
    rb_f_sprintf(int argc, const VALUE *argv)
    {
        return rb_str_format(argc - 1, argv + 1, GETNTHARG(0));
    }
                
    srand(number = Random.new_seed) → old_seed click to toggle source

    Seeds the system pseudo-random number generator, Random::DEFAULT, with number. The previous seed value is returned.

    If number is omitted, seeds the generator using a source of entropy provided by the operating system, if available (/dev/urandom on Unix systems or the RSA cryptographic provider on Windows), which is then combined with the time, the process id, and a sequence number.

    srand may be used to ensure repeatable sequences of pseudo-random numbers between different runs of the program. By setting the seed to a known value, programs can be made deterministic during testing.

    srand 1234               # => 268519324636777531569100071560086917274
    [ rand, rand ]           # => [0.1915194503788923, 0.6221087710398319]
    [ rand(10), rand(1000) ] # => [4, 664]
    srand 1234               # => 1234
    [ rand, rand ]           # => [0.1915194503788923, 0.6221087710398319]
    
     
                   static VALUE
    rb_f_srand(int argc, VALUE *argv, VALUE obj)
    {
        VALUE seed, old;
        rb_random_t *r = &default_rand;
    
        if (argc == 0) {
            seed = random_seed();
        }
        else {
            rb_scan_args(argc, argv, "01", &seed);
        }
        old = r->seed;
        r->seed = rand_init(&r->mt, seed);
    
        return old;
    }
                
    sub(pattern, replacement) → $_ click to toggle source
    sub(pattern) {|...| block } → $_

    Equivalent to $_.sub(args), except that $_ will be updated if substitution occurs. Available only when -p/-n command line option specified.

     
                   static VALUE
    rb_f_sub(int argc, VALUE *argv)
    {
        VALUE str = rb_funcall_passing_block(uscore_get(), rb_intern("sub"), argc, argv);
        rb_lastline_set(str);
        return str;
    }
                
    syscall(num [, args...]) → integer click to toggle source

    Calls the operating system function identified by num and returns the result of the function or raises SystemCallError if it failed.

    Arguments for the function can follow num. They must be either String objects or Integer objects. A String object is passed as a pointer to the byte sequence. An Integer object is passed as an integer whose bit size is same as a pointer. Up to nine parameters may be passed (14 on the Atari-ST).

    The function identified by num is system dependent. On some Unix systems, the numbers may be obtained from a header file called syscall.h.

    syscall 4, 1, "hello\n", 6   # '4' is write(2) on our box
    

    produces:

    hello
    

    Calling syscall on a platform which does not have any way to an arbitrary system function just fails with NotImplementedError.

    Note: syscall is essentially unsafe and unportable. Feel free to shoot your foot. The DL (Fiddle) library is preferred for safer and a bit more portable programming.

     
                   static VALUE
    rb_f_syscall(int argc, VALUE *argv)
    {
    #ifdef atarist
        VALUE arg[13]; /* yes, we really need that many ! */
    #else
        VALUE arg[8];
    #endif
    #if SIZEOF_VOIDP == 8 && defined(HAVE___SYSCALL) && SIZEOF_INT != 8 /* mainly *BSD */
    # define SYSCALL __syscall
    # define NUM2SYSCALLID(x) NUM2LONG(x)
    # define RETVAL2NUM(x) LONG2NUM(x)
    # if SIZEOF_LONG == 8
        long num, retval = -1;
    # elif SIZEOF_LONG_LONG == 8
        long long num, retval = -1;
    # else
    #  error ---->> it is asserted that __syscall takes the first argument and returns retval in 64bit signed integer. <<----
    # endif
    #elif defined(__linux__)
    # define SYSCALL syscall
    # define NUM2SYSCALLID(x) NUM2LONG(x)
    # define RETVAL2NUM(x) LONG2NUM(x)
        /*
         * Linux man page says, syscall(2) function prototype is below.
         *
         *     int syscall(int number, ...);
         *
         * But, it's incorrect. Actual one takes and returned long. (see unistd.h)
         */
        long num, retval = -1;
    #else
    # define SYSCALL syscall
    # define NUM2SYSCALLID(x) NUM2INT(x)
    # define RETVAL2NUM(x) INT2NUM(x)
        int num, retval = -1;
    #endif
        int i;
    
        if (RTEST(ruby_verbose)) {
            rb_warning("We plan to remove a syscall function at future release. DL(Fiddle) provides safer alternative.");
        }
    
        if (argc == 0)
            rb_raise(rb_eArgError, "too few arguments for syscall");
        if (argc > numberof(arg))
            rb_raise(rb_eArgError, "too many arguments for syscall");
        num = NUM2SYSCALLID(argv[0]); ++argv;
        for (i = argc - 1; i--; ) {
            VALUE v = rb_check_string_type(argv[i]);
    
            if (!NIL_P(v)) {
                SafeStringValue(v);
                rb_str_modify(v);
                arg[i] = (VALUE)StringValueCStr(v);
            }
            else {
                arg[i] = (VALUE)NUM2LONG(argv[i]);
            }
        }
    
        switch (argc) {
          case 1:
            retval = SYSCALL(num);
            break;
          case 2:
            retval = SYSCALL(num, arg[0]);
            break;
          case 3:
            retval = SYSCALL(num, arg[0],arg[1]);
            break;
          case 4:
            retval = SYSCALL(num, arg[0],arg[1],arg[2]);
            break;
          case 5:
            retval = SYSCALL(num, arg[0],arg[1],arg[2],arg[3]);
            break;
          case 6:
            retval = SYSCALL(num, arg[0],arg[1],arg[2],arg[3],arg[4]);
            break;
          case 7:
            retval = SYSCALL(num, arg[0],arg[1],arg[2],arg[3],arg[4],arg[5]);
            break;
          case 8:
            retval = SYSCALL(num, arg[0],arg[1],arg[2],arg[3],arg[4],arg[5],arg[6]);
            break;
    #ifdef atarist
          case 9:
            retval = SYSCALL(num, arg[0],arg[1],arg[2],arg[3],arg[4],arg[5],arg[6],
              arg[7]);
            break;
          case 10:
            retval = SYSCALL(num, arg[0],arg[1],arg[2],arg[3],arg[4],arg[5],arg[6],
              arg[7], arg[8]);
            break;
          case 11:
            retval = SYSCALL(num, arg[0],arg[1],arg[2],arg[3],arg[4],arg[5],arg[6],
              arg[7], arg[8], arg[9]);
            break;
          case 12:
            retval = SYSCALL(num, arg[0],arg[1],arg[2],arg[3],arg[4],arg[5],arg[6],
              arg[7], arg[8], arg[9], arg[10]);
            break;
          case 13:
            retval = SYSCALL(num, arg[0],arg[1],arg[2],arg[3],arg[4],arg[5],arg[6],
              arg[7], arg[8], arg[9], arg[10], arg[11]);
            break;
          case 14:
            retval = SYSCALL(num, arg[0],arg[1],arg[2],arg[3],arg[4],arg[5],arg[6],
              arg[7], arg[8], arg[9], arg[10], arg[11], arg[12]);
            break;
    #endif
        }
    
        if (retval == -1)
            rb_sys_fail(0);
        return RETVAL2NUM(retval);
    #undef SYSCALL
    #undef NUM2SYSCALLID
    #undef RETVAL2NUM
    }
                
    system([env,] command... [,options]) → true, false or nil click to toggle source

    Executes command… in a subshell. command… is one of following forms.

    commandline                 : command line string which is passed to the standard shell
    cmdname, arg1, ...          : command name and one or more arguments (no shell)
    [cmdname, argv0], arg1, ... : command name, argv[0] and zero or more arguments (no shell)

    system returns true if the command gives zero exit status, false for non zero exit status. Returns nil if command execution fails. An error status is available in $?. The arguments are processed in the same way as for Kernel.spawn.

    The hash arguments, env and options, are same as exec and spawn. See Kernel.spawn for details.

    system("echo *")
    system("echo", "*")
    

    produces:

    config.h main.rb
    *

    See Kernel.exec for the standard shell.

     
                   static VALUE
    rb_f_system(int argc, VALUE *argv)
    {
        rb_pid_t pid;
        int status;
    
    #if defined(SIGCLD) && !defined(SIGCHLD)
    # define SIGCHLD SIGCLD
    #endif
    
    #ifdef SIGCHLD
        RETSIGTYPE (*chfunc)(int);
    
        rb_last_status_clear();
        chfunc = signal(SIGCHLD, SIG_DFL);
    #endif
        pid = rb_spawn_internal(argc, argv, NULL, 0);
    #if defined(HAVE_WORKING_FORK) || defined(HAVE_SPAWNV)
        if (pid > 0) {
            int ret, status;
            ret = rb_waitpid(pid, &status, 0);
            if (ret == (rb_pid_t)-1)
                rb_sys_fail("Another thread waited the process started by system().");
        }
    #endif
    #ifdef SIGCHLD
        signal(SIGCHLD, chfunc);
    #endif
        if (pid < 0) {
            return Qnil;
        }
        status = PST2INT(rb_last_status_get());
        if (status == EXIT_SUCCESS) return Qtrue;
        return Qfalse;
    }
                
    test(cmd, file1 [, file2] ) → obj click to toggle source

    Uses the character cmd to perform various tests on file1 (first table below) or on file1 and file2 (second table).

    File tests on a single file:

    Cmd    Returns   Meaning
    "A"  | Time    | Last access time for file1
    "b"  | boolean | True if file1 is a block device
    "c"  | boolean | True if file1 is a character device
    "C"  | Time    | Last change time for file1
    "d"  | boolean | True if file1 exists and is a directory
    "e"  | boolean | True if file1 exists
    "f"  | boolean | True if file1 exists and is a regular file
    "g"  | boolean | True if file1 has the \CF{setgid} bit
         |         | set (false under NT)
    "G"  | boolean | True if file1 exists and has a group
         |         | ownership equal to the caller's group
    "k"  | boolean | True if file1 exists and has the sticky bit set
    "l"  | boolean | True if file1 exists and is a symbolic link
    "M"  | Time    | Last modification time for file1
    "o"  | boolean | True if file1 exists and is owned by
         |         | the caller's effective uid
    "O"  | boolean | True if file1 exists and is owned by
         |         | the caller's real uid
    "p"  | boolean | True if file1 exists and is a fifo
    "r"  | boolean | True if file1 is readable by the effective
         |         | uid/gid of the caller
    "R"  | boolean | True if file is readable by the real
         |         | uid/gid of the caller
    "s"  | int/nil | If file1 has nonzero size, return the size,
         |         | otherwise return nil
    "S"  | boolean | True if file1 exists and is a socket
    "u"  | boolean | True if file1 has the setuid bit set
    "w"  | boolean | True if file1 exists and is writable by
         |         | the effective uid/gid
    "W"  | boolean | True if file1 exists and is writable by
         |         | the real uid/gid
    "x"  | boolean | True if file1 exists and is executable by
         |         | the effective uid/gid
    "X"  | boolean | True if file1 exists and is executable by
         |         | the real uid/gid
    "z"  | boolean | True if file1 exists and has a zero length

    Tests that take two files:

    "-"  | boolean | True if file1 and file2 are identical
    "="  | boolean | True if the modification times of file1
         |         | and file2 are equal
    "<"  | boolean | True if the modification time of file1
         |         | is prior to that of file2
    ">"  | boolean | True if the modification time of file1
         |         | is after that of file2
     
                   static VALUE
    rb_f_test(int argc, VALUE *argv)
    {
        int cmd;
    
        if (argc == 0) rb_check_arity(argc, 2, 3);
        cmd = NUM2CHR(argv[0]);
        if (cmd == 0) {
          unknown:
            /* unknown command */
            if (ISPRINT(cmd)) {
                rb_raise(rb_eArgError, "unknown command '%s%c'", cmd == '\'' || cmd == '\\' ? "\\" : "", cmd);
            }
            else {
                rb_raise(rb_eArgError, "unknown command \"\\x%02X\"", cmd);
            }
        }
        if (strchr("bcdefgGkloOprRsSuwWxXz", cmd)) {
            CHECK(1);
            switch (cmd) {
              case 'b':
                return rb_file_blockdev_p(0, argv[1]);
    
              case 'c':
                return rb_file_chardev_p(0, argv[1]);
    
              case 'd':
                return rb_file_directory_p(0, argv[1]);
    
              case 'e':
                return rb_file_exist_p(0, argv[1]);
    
              case 'f':
                return rb_file_file_p(0, argv[1]);
    
              case 'g':
                return rb_file_sgid_p(0, argv[1]);
    
              case 'G':
                return rb_file_grpowned_p(0, argv[1]);
    
              case 'k':
                return rb_file_sticky_p(0, argv[1]);
    
              case 'l':
                return rb_file_symlink_p(0, argv[1]);
    
              case 'o':
                return rb_file_owned_p(0, argv[1]);
    
              case 'O':
                return rb_file_rowned_p(0, argv[1]);
    
              case 'p':
                return rb_file_pipe_p(0, argv[1]);
    
              case 'r':
                return rb_file_readable_p(0, argv[1]);
    
              case 'R':
                return rb_file_readable_real_p(0, argv[1]);
    
              case 's':
                return rb_file_size_p(0, argv[1]);
    
              case 'S':
                return rb_file_socket_p(0, argv[1]);
    
              case 'u':
                return rb_file_suid_p(0, argv[1]);
    
              case 'w':
                return rb_file_writable_p(0, argv[1]);
    
              case 'W':
                return rb_file_writable_real_p(0, argv[1]);
    
              case 'x':
                return rb_file_executable_p(0, argv[1]);
    
              case 'X':
                return rb_file_executable_real_p(0, argv[1]);
    
              case 'z':
                return rb_file_zero_p(0, argv[1]);
            }
        }
    
        if (strchr("MAC", cmd)) {
            struct stat st;
            VALUE fname = argv[1];
    
            CHECK(1);
            if (rb_stat(fname, &st) == -1) {
                int e = errno;
                FilePathValue(fname);
                rb_syserr_fail_path(e, fname);
            }
    
            switch (cmd) {
              case 'A':
                return stat_atime(&st);
              case 'M':
                return stat_mtime(&st);
              case 'C':
                return stat_ctime(&st);
            }
        }
    
        if (cmd == '-') {
            CHECK(2);
            return rb_file_identical_p(0, argv[1], argv[2]);
        }
    
        if (strchr("=<>", cmd)) {
            struct stat st1, st2;
            struct timespec t1, t2;
    
            CHECK(2);
            if (rb_stat(argv[1], &st1) < 0) return Qfalse;
            if (rb_stat(argv[2], &st2) < 0) return Qfalse;
    
            t1 = stat_mtimespec(&st1);
            t2 = stat_mtimespec(&st2);
    
            switch (cmd) {
              case '=':
                if (t1.tv_sec == t2.tv_sec && t1.tv_nsec == t2.tv_nsec) return Qtrue;
                return Qfalse;
    
              case '>':
                if (t1.tv_sec > t2.tv_sec) return Qtrue;
                if (t1.tv_sec == t2.tv_sec && t1.tv_nsec > t2.tv_nsec) return Qtrue;
                return Qfalse;
    
              case '<':
                if (t1.tv_sec < t2.tv_sec) return Qtrue;
                if (t1.tv_sec == t2.tv_sec && t1.tv_nsec < t2.tv_nsec) return Qtrue;
                return Qfalse;
            }
        }
        goto unknown;
    }
                
    throw(tag [, obj]) click to toggle source

    Transfers control to the end of the active catch block waiting for tag. Raises UncaughtThrowError if there is no catch block for the tag. The optional second parameter supplies a return value for the catch block, which otherwise defaults to nil. For examples, see Kernel::catch.

     
                   static VALUE
    rb_f_throw(int argc, VALUE *argv)
    {
        VALUE tag, value;
    
        rb_scan_args(argc, argv, "11", &tag, &value);
        rb_throw_obj(tag, value);
        UNREACHABLE;
    }
                
    trace_var(symbol, cmd ) → nil click to toggle source
    trace_var(symbol) {|val| block } → nil

    Controls tracing of assignments to global variables. The parameter symbol identifies the variable (as either a string name or a symbol identifier). cmd (which may be a string or a Proc object) or block is executed whenever the variable is assigned. The block or Proc object receives the variable's new value as a parameter. Also see Kernel::untrace_var.

    trace_var :$_, proc {|v| puts "$_ is now '#{v}'" }
    $_ = "hello"
    $_ = ' there'
    

    produces:

    $_ is now 'hello'
    $_ is now ' there'
     
                   VALUE
    rb_f_trace_var(int argc, const VALUE *argv)
    {
        VALUE var, cmd;
        struct rb_global_entry *entry;
        struct trace_var *trace;
    
        if (rb_scan_args(argc, argv, "11", &var, &cmd) == 1) {
    	cmd = rb_block_proc();
        }
        if (NIL_P(cmd)) {
    	return rb_f_untrace_var(argc, argv);
        }
        entry = rb_global_entry(rb_to_id(var));
        if (OBJ_TAINTED(cmd)) {
    	rb_raise(rb_eSecurityError, "Insecure: tainted variable trace");
        }
        trace = ALLOC(struct trace_var);
        trace->next = entry->var->trace;
        trace->func = rb_trace_eval;
        trace->data = cmd;
        trace->removed = 0;
        entry->var->trace = trace;
    
        return Qnil;
    }
                
    trap( signal, command ) → obj click to toggle source
    trap( signal ) {| | block } → obj

    Specifies the handling of signals. The first parameter is a signal name (a string such as “SIGALRM”, “SIGUSR1”, and so on) or a signal number. The characters “SIG” may be omitted from the signal name. The command or block specifies code to be run when the signal is raised. If the command is the string “IGNORE” or “SIG_IGN”, the signal will be ignored. If the command is “DEFAULT” or “SIG_DFL”, the Ruby’s default handler will be invoked. If the command is “EXIT”, the script will be terminated by the signal. If the command is “SYSTEM_DEFAULT”, the operating system’s default handler will be invoked. Otherwise, the given command or block will be run. The special signal name “EXIT” or signal number zero will be invoked just prior to program termination. trap returns the previous handler for the given signal.

    Signal.trap(0, proc { puts "Terminating: #{$$}" })
    Signal.trap("CLD")  { puts "Child died" }
    fork && Process.wait
    

    produces:

    Terminating: 27461
    Child died
    Terminating: 27460
     
                   static VALUE
    sig_trap(int argc, VALUE *argv)
    {
        int sig;
        sighandler_t func;
        VALUE cmd;
    
        rb_check_arity(argc, 1, 2);
    
        sig = trap_signm(argv[0]);
        if (reserved_signal_p(sig)) {
            const char *name = signo2signm(sig);
            if (name)
                rb_raise(rb_eArgError, "can't trap reserved signal: SIG%s", name);
            else
                rb_raise(rb_eArgError, "can't trap reserved signal: %d", sig);
        }
    
        if (argc == 1) {
            cmd = rb_block_proc();
            func = sighandler;
        }
        else {
            cmd = argv[1];
            func = trap_handler(&cmd, sig);
        }
    
        if (OBJ_TAINTED(cmd)) {
            rb_raise(rb_eSecurityError, "Insecure: tainted signal trap");
        }
    
        return trap(sig, func, cmd);
    }
                
    untrace_var(symbol [, cmd] ) → array or nil click to toggle source

    Removes tracing for the specified command on the given global variable and returns nil. If no command is specified, removes all tracing for that variable and returns an array containing the commands actually removed.

     
                   VALUE
    rb_f_untrace_var(int argc, const VALUE *argv)
    {
        VALUE var, cmd;
        ID id;
        struct rb_global_entry *entry;
        struct trace_var *trace;
        VALUE data;
    
        rb_scan_args(argc, argv, "11", &var, &cmd);
        id = rb_check_id(&var);
        if (!id) {
    	rb_name_error_str(var, "undefined global variable %"PRIsVALUE"", QUOTE(var));
        }
        if (!rb_id_table_lookup(rb_global_tbl, id, &data)) {
    	rb_name_error(id, "undefined global variable %"PRIsVALUE"", QUOTE_ID(id));
        }
    
        trace = (entry = (struct rb_global_entry *)data)->var->trace;
        if (NIL_P(cmd)) {
    	VALUE ary = rb_ary_new();
    
    	while (trace) {
    	    struct trace_var *next = trace->next;
    	    rb_ary_push(ary, (VALUE)trace->data);
    	    trace->removed = 1;
    	    trace = next;
    	}
    
    	if (!entry->var->block_trace) remove_trace(entry->var);
    	return ary;
        }
        else {
    	while (trace) {
    	    if (trace->data == cmd) {
    		trace->removed = 1;
    		if (!entry->var->block_trace) remove_trace(entry->var);
    		return rb_ary_new3(1, cmd);
    	    }
    	    trace = trace->next;
    	}
        }
        return Qnil;
    }
                
    warn(msg, ...) → nil click to toggle source

    Displays each of the given messages followed by a record separator on STDERR unless warnings have been disabled (for example with the -W0 flag).

      warn("warning 1", "warning 2")
    
    <em>produces:</em>
    
      warning 1
      warning 2
     
                   static VALUE
    rb_warn_m(int argc, VALUE *argv, VALUE exc)
    {
        if (!NIL_P(ruby_verbose) && argc > 0) {
            rb_io_puts(argc, argv, rb_stderr);
        }
        return Qnil;
    }