Running shell is wrong when called from script

[barefootcoder]

If you call a Perl program using Shell::Guess->running_shell from inside a (say) bash script, it returns the shell of the command line used to launch the script as opposed to bash. This is because the method used by running_shell pulls the whole command line out of the file in the /proc system, but doesn't restrict what it looks at to arg 0.

A simple command to demonstrate this:

> tcsh -c 'bash -c "'"perl -MShell::Guess -le 'print Shell::Guess->running_shell->name'"\"
tc

That should really return bash. I'm not sure how to turn this into a useful test, however, since the test suite needs to run on all OSes.

The patch is simple:

diffing ./common/perl/Shell/Guess.pm against ./perl5/perlbrew/perls/perl-5.14.4/lib/site_perl/5.14.4/Shell/Guess.pm
57c57
<     $command_line =~ s/\0$//;

---
>     $command_line =~ s/\0.*$//;

or I could turn that into a pull request if that's easier.

[plicease]

I think you are right. Let me give it some thought probably next week I can spend an hour or two to address it.

Any test for this can be skipped on OSes that don't have a /proc.

[plicease]

So I have pushed out a dev version with this change as 0.02_01 on CPAN

If it still looks good in a few days I will promote this to a regular release.

Interestingly, with your particular example, I am still not getting bash:

iscah% tcsh -c 'bash -c "'"perl -MShell::Guess -le 'print Shell::Guess->running_shell->name'"\"
c

when I stepped through in the debugger I was seeing this as the parent command line:

  DB<1> x $command_line
0  "-csh\c@-c\c@bash -c \"perl -d -MShell::Guess -le 'print Shell::Guess->running_shell->name'\"\c@"

So I think bash must be doing an exec to execute Perl in this case, which I think is mostly impossible to defend against.

[plicease]

On CPAN as 0.03

[barefootcoder]

So I think bash must be doing an exec to execute Perl in this case, which I think is mostly impossible to defend against.

You're probably right there; I was trying to compact a test case into a one-liner there, but perhaps I didn't test thoroughly enough. A more realistic test would be to create, say, a bash script like so:

#! /bin/bash

perl -MShell::Guess -le 'print Shell::Guess->running_shell->name'

and then run that script from, say, tcsh.

IAE, your new version definitely fixes the issue, so thanx for the quick turnaround!