jeanluca has asked for the wisdom of the Perl Monks concerning the following question:

Dear Monks

I wrote the following test program to cat 2 files (at some point I will write a module that can (also) concatenate binary files)
#! /usr/bin/perl -lw

use strict ;

use File::Cat;

open OUT,">o3" ;
cat ('o1', *OUT ) or die "Can't cat o1: $!";
cat ('o2', *OUT ) or die "Can't cat o2: $!";
close OUT ;

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When I do a more on file o3 I see
this line is from o1

this line is from o2

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When I remove the -l option on the first line I get 
this line is from o1
this line is from o2

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So the empty lines are introduced by this option, and is not from the files.
To me this looks like a bug, but I have to add that when I do say things like this its probably a very important feature!
Anyway, is there a way I can turn this option of for a specific code block or for a whole module ?

Thnx LuCa

Replies are listed 'Best First'.
Re: problem with File::Cat
by lidden (Curate) on Apr 24, 2007 at 12:14 UTC
    Yes it is a nice feature see "perldoc perlrun"

    What did you expect the -l option to do when you added it?

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      Or, from the man page:

      It has two separate effects. First, it automatically chomps $/ (the input record separator) when used with -n or -p. Second, it assigns "$\" (the output record separator) to have the value of octnum so that any print statements will have that separator added back on. If octnum is omitted, sets "$\" to the current value of $/.

      Or, in the vernacular, if you include the -l option, it will add an end-of-line to each print.

      --
      tbone1, YAPS (Yet Another Perl Schlub)
      And remember, if he succeeds, so what.
      - Chick McGee

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      Don't get me wrong, the -l is very nice, but not when you cat files (especially not with binary files)!
      I cannot think of a situation in which this kind of behavior can be useful!!

      Anyway from the suggested docs the answer to my problems was simple 
      { local $\ ;
    # do 'cat' stuff here
}

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      Thanks a lot
      LuCa

      UPDATE: I checked the code from the cpan module File::Cat and I would suggest to change the following 
          while (<FILE>) {
        print $handle $_;
    }

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      into
          while (<FILE>) {
        printf $handle $_;
    }

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      (not tested)
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[d/l]
[select]
        You definitely do not want to use printf like that!   The second argument in your example is the format string so any % characters in it will be interpreted by printf.
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[d/l]

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