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

In my line of work, it seems that more often that not I write a script that contains functionality that would be useful to have as part of a module as well. While I could certainly put all of my useful code in a module and then write a short wrapper that would call a routine in the module to kick off processing, I think that it would be slick if I could make it all happen in the module file. For example, I have a module called checkem.pm that starts off as follows: 
#!/bin/sh

eval "exec /usr/software/bin/perl5.8.0 -I`pwd` -Mcheckem -e main $*"
    if $running_under_some_shell;

package main;

sub main {
    print "Hello from main\n";
    <useful code here>
}

[download]
This is all well and good, but it requires me to be in the directory where checkem.pm lives or to hardcode the path to checkem.pm in the -I argument. Neither of these is horribly appealing to me. It would be really nice if I could use the same code in each module. I was trying to do something more like: 
#!/bin/sh

DIR=`dirname $0`
BASE=`basename $0 | sed -e 's/\.pm\$//'`
eval "exec /usr/software/bin/perl5.8.0 -I$DIR -M$BASE -e main $*"
    if $running_under_some_shell;

package main;
...

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but of course Perl doesn't like the DIR= and BASE=lines. Adding if $running_under_some_shell to the DIR= and BASE= lines doesn't help either and -w didn't provide any useful insight. Any suggestions would be appreciated. It would also be nice if I didn't have to name things module.pm too ;-)

Replies are listed 'Best First'.
Re: Running a module?
by abell (Chaplain) on Sep 19, 2003 at 14:16 UTC

    Whether you have been called as a script or included as a module can be checked by taking a look at caller.

    A small example: 

    #!/usr/bin/perl

package mymodule;

use Data::Dumper;

my @caller = caller;
print Dumper ( @caller );

print "Execute this\n" unless caller;

1;

    [download]
    When called as perl mymodule.pm this outputs 
    
Execute this
    while when called as perl -Mmymodule -e '' it outputs 
    
$VAR1 = 'main';
$VAR2 = '-e';
$VAR3 = 0;

    Cheers

    Antonio

    The stupider the astronaut, the easier it is to win the trip to Vega - A. Tucket
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Re: Running a module?
by Abigail-II (Bishop) on Sep 19, 2003 at 14:21 UTC 
    #!/bin/sh

eval "exec /opt/perl/bin/perl -I`dirname $0` -M`basename $0 .pm` -e ma
+in $*"
    if $running_under_some_shell;

package main;

sub main {
    print "Hello from main\n";
}

1;

    [download]

    That seems to work for me.

    Abigail

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[d/l]
      Duh, must have too much water on the brain. Now if I could just get perl to load a module that doesn't end in .pm life would be perfect.
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        BEGIN{ require "Foo.baz"; Foo->import(); }

        [download]
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[d/l]
        #!/bin/sh

eval "exec /opt/perl/bin/perl -I`dirname $0` -e 'require q!base!; main
+ ()' $*"  
    if $running_under_some_shell;
    
package main;

sub main {
    print "Hello from main\n";
}
 
1;

        [download]

        Abigail

[reply]
[d/l]
Re: Running a module?
by dtr (Scribe) on Sep 19, 2003 at 14:23 UTC

    You can use the FindBin module to get the path to the executable you are currently running.

    Try:-

    BEGIN {
  use FindBin qw( $BIN );
  use lib qw( $BIN );
}

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    Or, if that doesn't work for you:-
    #! /user/bin/perl -I .
BEGIN {
  use FindBin qw( $BIN );
  chdir $BIN;
}

    [download]
    might also work for you.

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