http://qs1969.pair.com?node_id=2878


in reply to Return the contents of a file

Two things:

1) that while loop should read: 

   while (<FS>) { $OP .= $_ }

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Note the all-important ".=" instead of "=" (probably just a mistype on your part. :)

2) your opens should always check for error messages, and you should get faster results slurping the whole file in as one string, like so: 

    sub readfile {
        my $OP;
        open FS, $_[0] or die "Can't open $_[0]: $!";
        {
            local $/ = undef;
            $OP = <FS>;
        }
        close FS or die "Can't close $_[0]: $!";
        return $OP;
    }

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Replies are listed 'Best First'.
RE: Return the contents of a file
by turnstep (Parson) on Apr 12, 2000 at 18:02 UTC

    Here's another version: 

    sub readfile {
  local $/="" unless wantarray;
  return open(FS, shift) ? <FS> : undef;
}

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    No 'my' variables, handles both string and array requests, and returns undef if the file could not be opened. Use it like this:

    defined($slurp = &readfile($file)) or die "Could not open $file: $!\n"
+;
print "Scalar 'slurp' now has ", length $slurp, " characters in it\n";
defined(@slurp = &readfile($file)) or die "Could not open $file: $!\n"
+;
print "Array 'slurp' now has ", $#slurp, " elements in it.\n";

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      WOW!
      Just loves to see this.
      -anders
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RE: RE: Return the contents of a file
by Chris (Novice) on Apr 12, 2000 at 05:50 UTC
    I REALLY do like this one. I've found that it works great for small files. Has anyone had any experiences using this technique w/ something large like a *.cvs file from a database dump? Are there any memory issues to handling a variable that large. -- I shouldn't thinks so. Hmmm...
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      There *are* memory issues in having very large variables, just as there would be, presumably, in any language. Perl variables take up a lot of space. From perlfaq3: 
          When it comes to time-space tradeoffs, Perl nearly
    always prefers to throw memory at a problem. Scalars
    in Perl use more memory than strings in C, arrays
    take more that, and hashes use even more.

      [download]
      I mean, if you *can* process a file line by line, it's best to do so.
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In Section Cool Uses for Perl