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Re^2: <> oddity ?

by hdb (Monsignor)
on Mar 27, 2013 at 10:31 UTC ( #1025669=note: print w/replies, xml ) Need Help??

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

If you call the code below,

while(<>) { print; }

then all three commands below result in the same output:

$ perl $ perl < $ cat | perl

Replies are listed 'Best First'.
Re^3: <> oddity ?
by LanX (Sage) on Mar 27, 2013 at 10:48 UTC
    you're right

    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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