http://qs1969.pair.com?node_id=800812

myuserid7 has asked for the wisdom of the Perl Monks concerning the following question:

I recently moved to CSW blastwave repositories - including perl.

I have a perl script that accepts a C program and does a pretty print to a network printer using lp().

The postscript is capture in a HERE doc. 

$prolog = << ENDPROLOG;
.
.
.
A bunch of postscript.
.
.
.
ENDPROLOG

$PRINT_CMD = '/usr/bin/lp';
$outcmd = "| $PRINT_CMD";

open(OUT,$outcmd);

print OUT $prolog;

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After upgrading perl the script is no longer printing the postscript but is printing the postscript code.

I was wondering if someone could point me to a better way.

Replies are listed 'Best First'.
Re: piping to lp is broken after perl upgrade
by moritz (Cardinal) on Oct 12, 2009 at 22:29 UTC

    You should check if open was successful, and also if close was: 

    open my $output, '|-', $PRINT_CMD
    or die "Can't open pipe to $PRINT_CMD: $!";
print $output $prolog;
...
close $output or warn "Error while closing pipe to $PRINT_CMD: $!";

    [download]

    Maybe that'll give you some clue about what's wrong.

    Perl 6 - links to (nearly) everything that is Perl 6.
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[d/l]
      I got excited when I saw your close - I thought for sure the open handle was causing the grief.

      Added the error checking. Nothing.

      Something is foobar here and I am not sure it is perl. Even from the command line... 

      cat foo.ps | /usr/bin/lp -o nobanner

      [download]
      prints the postscript code while... 
      /usr/bin/lp -o nobanner foo.ps

      [download]
      Prints the postscript document. So I really can't expect my perl script to work as written.
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[d/l]
[select]
Re: piping to lp is broken after perl upgrade
by GrandFather (Saint) on Oct 13, 2009 at 00:34 UTC

    I don't see an issue in the code you've shown except that you're not using strictures (use strict; use warnings;). It wouldn't surprise me a great deal to find that there is something that was waiting in your heredoc to bite and has now bitten. It may help if you:

    my $prolog = << 'ENDPROLOG';

    [download]

    so interpolation doesn't happen.

    True laziness is hard work
[reply]
[d/l]
      Thanks for your reply.

      I created a files called test.ps. 

      $ cat test.ps 
%!PS
/Courier findfont
20 scalefont
setfont
72 500 moveto
(Hello world!) show
showpage

      [download]
      If I send it to the printer, it works. I get a Hello World.

      So here is a recreation of the script that is failing. 

      #!/opt/csw/bin/perl -w

use strict;
use warnings;

my $prolog = <<ENDPROLOG;
%!PS
/Courier findfont
20 scalefont
setfont
72 500 moveto
(Hello world!) show
showpage
ENDPROLOG
my $PRINT_CMD = '/usr/bin/lp -o nobanner';
open my $output, '|-', $PRINT_CMD
    or die "Can't open pipe to $PRINT_CMD: $!";
print $output $prolog;
close $output or warn "Error while closing pipe to $PRINT_CMD: $!";

      [download]
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[d/l]
[select]
        I ended up abandoning the use the csw perl for this script. Instead, I pulled the 5.8.9 source and complied it on my Solaris 10 machine using gcc4.

        I pointed the test script at the new compile and it started working.

        Sadly, I am not that confident in the blastwave perl now. Surely just paranoia but once bitten...

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