readline
- readline EXPR
- readline
Reads from the filehandle whose typeglob is contained in EXPR (or from
*ARGV
if EXPR is not provided). In scalar context, each call reads and returns the next line until end-of-file is reached, whereupon the subsequent call returnsundef
. In list context, reads until end-of-file is reached and returns a list of lines. Note that the notion of "line" used here is whatever you may have defined with$/
or$INPUT_RECORD_SEPARATOR
). See $/ in perlvar.When
$/
is set toundef
, whenreadline
is in scalar context (i.e., file slurp mode), and when an empty file is read, it returns''
the first time, followed byundef
subsequently.This is the internal function implementing the
<EXPR>
operator, but you can use it directly. The<EXPR>
operator is discussed in more detail in I/O Operators in perlop.- $line = <STDIN>;
- $line = readline(*STDIN); # same thing
If
readline
encounters an operating system error,$!
will be set with the corresponding error message. It can be helpful to check$!
when you are reading from filehandles you don't trust, such as a tty or a socket. The following example uses the operator form ofreadline
and dies if the result is not defined.Note that you have can't handle
readline
errors that way with theARGV
filehandle. In that case, you have to open each element of@ARGV
yourself sinceeof
handlesARGV
differently.