reseting PATH

[Anonymous Monk]

I have a problem in pre-pending to PATH for a captive script. I'm trying to append the location of the perl executable I wish to use to the beginning of the PATH and then exec it to pick up the change. Since this perl script is called directly in a captive environment I am unable to set these environment variables in calling script first. This method works fine for other environment variables (I picked this code up from a response to another question by Tye) but not for the PATH.

# Set up the perl executable and library path
BEGIN {
        $ENV{PATH} = "/mypath/perl/bin:$ENV{PATH}";
        $ENV{PERL5LIB} = '/mypath/perl/lib/site_perl/5.8.8/sun4-solari
+s:/mypath/perl/lib/site_perl/5.8.8:/mypath/perl/lib/site_perl:/mypath
+/perl/lib/5.8.8:/mypath/perl/lib/site_perl';
        exec 'env', $^X, $0, @ARGV;
}

The problem is that when I do the above the executable never returns and I cannot figure out what it is doing. I suspect it is constantly re executing itself in an infinite loop
Any help appreciated

[Corion]

How will your Perl program know that it has already re-executed itself?

My approach would be to set a second environment variable to tell your program that it is already re-executing:

warn "$0 launched";
if (! $ENV{RE_EXECUTING}) {
    $ENV{RE_EXECUTING} = 1;
    warn "Set up environment. Re-executing now.";
    exec ...
};

But maybe you want to just check whether the environment needs changing at all, and only if you need changes re-execute?

[Anonymous Monk]

Thanks. I knew the answer was staring me in the face.

[ikegami]

I think it's safer to pass an argument.

Secondly, env $^X makes no sense. You want one of

• exec $^X, ...
• exec 'env', 'perl', ...
• exec '/mypath/perl/bin/perl', ...

Your other changes would indicate you want the last.

Thirdly, the changes to PERL5LIB look redundant with the paths built into the Perl you want to be running.

BEGIN {
    if (@ARGV && $ARGV[0] eq '--fixed') {
        shift(@ARGV);
    } else {
        $ENV{PATH} = join ':', '/mypath/perl/bin', $ENV{PATH};
        delete $ENV{PERL5LIB};
        exec '/mypath/perl/bin/perl', $0, '--fixed', @ARGV;
        die ...;
    }
}