Re^2: <> oddity ?


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Re^2: <> oddity ?

by hdb (Monsignor)

on Mar 27, 2013 at 10:31 UTC ( [id://1025669]=note: print w/replies, xml )

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in reply to Re: <> oddity ?
in thread <> oddity ?

If you call the code below stdin.pl,

while(<>) {
    print;
}
[download]

then all three commands below result in the same output:

$ perl stdin.pl stdin.pl
$ perl stdin.pl < stdin.pl
$ cat stdin.pl | perl stdin.pl
[download]

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Re^3: <> oddity ?
by LanX (Saint) on Mar 27, 2013 at 10:48 UTC

from perlop

       The null filehandle <> is special: it can be used to emulate the
       behavior of sed and awk.  Input from <> comes either from standard
       input, or from each file listed on the command line.  Here’s how it
       works: the first time <> is evaluated, the @ARGV array is checked, and
       if it is empty, $ARGV[0] is set to "-", which when opened gives you
       standard input.  The @ARGV array is then processed as a list of
       filenames.  The loop


           while (<>) {
               ...                     # code for each line
           }


       is equivalent to the following Perl-like pseudo code:


           unshift(@ARGV, '-') unless @ARGV;
           while ($ARGV = shift) {
               open(ARGV, $ARGV);
               while (<ARGV>) {
                   ...         # code for each line
               }
           }

Cheers Rolf

( addicted to the Perl Programming Language)

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