How to find out the location of the perl interpreter? First line always #!/usr/bin/perl?

[Mark Richards]

I can run perl scripts on certain computers with this first line:

#!/usr/bin/perl

However on other computers this does not work.

AFAIK this line represent the location of the perl interpreter.

How can I find out the correct path to the perl interpreter resp. which
path I have to enter in the first line ?

Mark

 

[Mark Shroyer]

I can run perl scripts on certain computers with this first line:

#!/usr/bin/perl

However on other computers this does not work.

AFAIK this line represent the location of the perl interpreter.

How can I find out the correct path to the perl interpreter resp. which
path I have to enter in the first line ?

Common practice is to use the following hashbang instead:

#!/usr/bin/env perl

or

#!/usr/bin/env perl -options

The utility env(1)'s purpose is ostensibly to run programs with
certain specified environment variable bindings, which are passed to
env as name=value pairs preceding the name of the command to run;
but when used this way, it simply execs the first copy of "perl"
that it finds on the path, passing it any options specified
thereafter.

On almost all modern, Unix-like (including Linux, *BSD, and OS X)
systems, env is either installed at /usr/bin/env or has a symbolic
link to it from that path. On older versions of Caldera OpenServer,
however, and maybe a couple other now-obscure operating systems,
there's only /bin/env; but the existence of /usr/bin/env is
widespread enough these days to make it an extremely portable (and
popular) choice.

On the Unix systems I regularly use, anyway (OpenBSD, OS X, and
Debian Linux), the hashbang has to specify a *full* interpreter
path, which is the reason why the name "perl" cannot simply be put
in there without proxying it through an absolutely-referenced
command in this manner.

 

[A. Sinan Unur]

....

On almost all modern, Unix-like (including Linux, *BSD, and OS X)
systems, env is either installed at /usr/bin/env or has a symbolic
link to it from that path.

On almost all modern, Unix-like (including Linux, *BSD, and OS X)
systems, system default perl is either installed at /usr/bin/perl
or has a symbolic link to it from that path.

Sinan

 

[Mark Shroyer]

On almost all modern, Unix-like (including Linux, *BSD, and OS X)
systems, system default perl is either installed at /usr/bin/perl
or has a symbolic link to it from that path.

Apparently not on the OP's computers, as you would learn if you took
the time to read his post. And hard-coding the interpreter to
/usr/bin/perl is a bad idea anyway, in case the user wants to
default to a different Perl installation in /usr/local or somewhere
else entirely.

 

[Ben Morrow]

Quoth (e-mail address removed):
which perl, on most Unix systems. Also, perl -V:startperl will tell you
the correct #! line to use, if perl could determine one. If it couldn't,
then perl -Verlpath will give you the full path to this perl.

The best answer, though, is to package up your scripts into a proper
distribution, and use the EXE_FILES parameter to ExtUtils::MakeMaker (or
equivalent for Module::Build or Module::Install), which will fixup the
#! line for you as required, including doing something appropriate for
systems that don't support #! at all.

Common practice is to use the following hashbang instead:

#!/usr/bin/env perl

This is a potential security risk: you are allowing the user of the
script to determine which perl is used. I don't know how env behaves
when setid or under sudo: unless you do, you shouldn't use this.

Ben

 

[xhoster]

I can run perl scripts on certain computers with this first line:

#!/usr/bin/perl

However on other computers this does not work.

AFAIK this line represent the location of the perl interpreter.

How can I find out the correct path to the perl interpreter resp. which
path I have to enter in the first line ?

Ask the system administrator.

Xho

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[A. Sinan Unur]

Apparently not on the OP's computers, as you would learn if you took
the time to read his post.

Well, if there is no /usr/bin/perl on the OP's system, what are the odds
that /usr/bin/env is there?

And hard-coding the interpreter to /usr/bin/perl is a
bad idea anyway, in case the user wants to
default to a different Perl installation in /usr/local or somewhere
else entirely.

That can be customized during installation.

Sinan