SPUG: finding full path to itself

DeRykus, Charles E charles.e.derykus at boeing.com
Wed May 31 09:36:49 PDT 2006


On Tue, May 30, 2006 at 02:36:20PM -0700, Satish Gupta wrote:
> When I a stand-alone script is running, how can this script determine 
> it's own absolute path in a portable manner?
> I notice that $0 works differently on different OS's. On some it gives

> full path and not on others.

>> Along those same lines how can I, in a portable manner, determine the
full path 
>> to the perl executable?

>> Kwiki has a hardcoded path of #!/usr/bin/perl which is okay for most
>> machines, but I'm stuck with a windows box for right now.  It is not
a big deal 
>> as I just edit index.cgi after every update (or I could edit the
Kwiki::Files file) 
>> but it would be nice to automagically figure that out when installing

The recommended safe way in `perldoc perl` is to use the installed
On Win32 for instance:

C:\>perl -V:perlpath

C:\>perl -V:_exe

>From `perldoc perlvar`:

    Because many operating systems permit anyone with
    read access to the Perl program file to make a copy
    of it, patch the copy, and then execute the copy,
    the security-conscious Perl programmer should take
    care to invoke the installed copy of perl, not the
    copy referenced by $^X.  The following statements
    accomplish this goal, and produce a pathname that
    can be invoked as a command or referenced as a file.

    use Config;
    $secure_perl_path = $Config{perlpath};
    if ($^O ne 'VMS')
      {$secure_perl_path .= $Config{_exe}
           unless $secure_perl_path =~ m/$Config{_exe}$/i;}

Charles DeRykus

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