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From: gson@blob.hut.fi (Andreas Gustafsson)
Newsgroups: comp.lang.perl
Subject: Problem with -i option and <> in array context
Message-ID: <1991May11.091442.11389@santra.uucp>
Date: 11 May 91 09:14:42 GMT
Sender: news@santra.uucp (Cnews - USENET news system)
Reply-To: gson@niksula.hut.fi (Andreas Gustafsson)
Organization: Helsinki University of Technology, Finland
Lines: 37

I am trying to munge some mailbox files in-place by using Perl with
the -i option.  The file is accessed in a somewhat random fashion, so
I want to read the whole file into an array using @array=<>.  It turns
out that this doesn't work very well with the -i option.  Consider the
following program:

#!/p/bin/perl -i.bak
@lines=<>;
for(@lines)
{ s/^/X /;
}
$;="\n";
print @lines;

When running the above program with a text file "foo" as an argument,
it correctly prepends "X " to each line in the file but instead of
modifying the file in-place it prints the modified file on standard
output, leaving an em does work as expected:
The following program, which does not use <> in an array context,

#!/p/bin/perl -i.bak
while(<>)
{ s/^/X /;
  print;
}

Versions 3.0pl37 and 4.003 both behave this way.  The man page says
that with -i, "files processed by the <> construct are to be edited
in-place", not "files processed by the _scalar_ <> construct ...".  Is
this a bug in Perl, a bug in the man page, or am I just doing
something wrong?

perl -i -e '@_=<>; print "Just another Perl hacker,\n";' /dev/null
--
Andreas Gustafsson
Internet: gson@niksula.hut.fi
Voice: +358 0 563 5592