comment on

In our installation, we have perl installed as a multi-platform setup:

   /net/tools/perl/perl-5.8.8/bin/perl   (wrapper)
   /net/tools/perl/perl-5.8.8/lib/...

   /net/tools/perl/perl-5.8.8/sparc/bin/perl
   /net/tools/perl/perl-5.8.8/i386/bin/perl
   /net/tools/perl/perl-5.8.8/linux/bin/perl
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The perl wrapper is a bourne shell script that runs "uname" to determine what architecture one is in, and then does an exec to the binary specific perl in either sparc (Solaris), i386 (Solaris), or linux. Scripts that use this installation, need to have custom shebang ("#!") headers, so that the script will run on any of the platforms. We're using this setup:

   #!/bin/sh --
   # -*- perl -*-
      eval 'exec /net/tools/perl/perl-5.8.8/bin/perl -xw $0 ${1+"$@"}'
         if 0;
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Using this format, our scripts can run without modification on any of our three platforms. There are numerous reasons why we've settled on this setup. Without Linux support, the header is simpler, and can just be as follows (Note the "perl" magic line can be added behind the bourne shell shebang, and the "-x" is not needed.):

   #!/bin/sh -- # -*- perl -*-
      eval 'exec /net/tools/perl/perl-5.8.8/bin/perl -w $0 ${1+"$@"}'
         if 0;
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The Linux bourne shell however doesn't allow arguments, so the "perl" magic string has to be commented as line #2, and then we have to add "-x" so that perl can figure out where it needs to start executing perl correctly. (Read perlrun for more information.) What I'm writing for advice and help with, is that when we try to debug a script with this header, the debugging structure croaks:

   % myscript.pl
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will run just fine. But to debug, we try this:

   % /net/tools/perl/perl-5.8.8/linux/bin/perl -d myscript.pl
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This doesn't work. It starts the debugger OK, but then tries to open "-d" as if it's a file. Here's the code:

% cat test-debug.pl
#!/bin/sh
#!-*- perl -*-
   eval 'exec /net/tools/perl/perl-5.8.8/bin/perl -wx $0 ${1+"$@"}'
     if 0;

print "$^X\n";
print "HI THERE\n";
exit;

% /net/tools/perl/perl-5.8.8/bin/perl -d test-debug.pl

Loading DB routines from perl5db.pl version 1.28
Editor support available.

Enter h or `h h' for help, or `man perldebug' for more help.

-d: bad option(s)
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This fails the same on all platforms.

So, any advice on how to improve this setup?

Here are some additional points:

The shebang magic works only if the files after the "#!" chars resolve to an executable ELF file. "/bin/sh" is such a program, as is "/net/tools/perl/perl-5.8.8/linux/bin/perl", or "/usr/bin/env". But our path to perl (/net/tools/perl/perl-5.8.8/bin/perl) is not a binary ELF program -- it's a script. So, we can't put this path behind "#!" -- we have to use the interpreted structure above where we can exec a script, as long as it's executable (doesn't have to be an ELF program).
The "#!" shebang magic seems to work differently for Linux as for Solaris. In Linux, #!/bin/sh can take no additional elements on the line.
We could use this pattern:
#!/usr/bin/env /net/tools/perl/perl-5.8.8/bin/perl
This works on all platforms, and also works with the debugger syntax. The drawback however, is that in linux, this doesn't allow any additional arguments after the COMMAND path element (i.e. "-w"). So, the warning flag has to be given with use warnings;

So, just curious if anyone in the Monastery has some special sauce that works for both Linux and Solaris... thanks! Cadphile...

In reply to multi-platform perl header for linux and solaris by cadphile

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