Bug #85757 for Argv: Argv finds external command even if environment is empty

Fri May 31 05:00:51 2013 dirk.heinrichs [...] altum.de - Ticket created

Subject:	Argv finds external command even if environment is empty
Date:	Fri, 31 May 2013 11:00:31 +0200
To:	bug-Argv [...] rt.cpan.org
From:	Dirk Heinrichs <dirk.heinrichs [...] altum.de>

Hello, don't know wether it's really a bug, but at least something I'd like to understand. I was testing a program that is using Argv for wether it can be used from cron, so I started it with env -i ./myprogram.pl to start it with an empty environment and found out it worked, although I used only the basename of the external programs I called via Argv. So my question is: Why is it working at all, given that the environment is empty? I was expecting that it failed with some kind of "No such file or directory" error. The following small program shows the behaviour: #!/usr/bin/perl use strict; use warnings; use Argv; my $cmd=Argv->new({autochomp=>1,autofail=>1,dbglevel=>2}); # Verify environment is empty print ("Environment:\n"); foreach my $key ( sort( keys(%ENV) ) ) { printf( "%s=%s\n", $key, $ENV{$key} ); } # Call external command print ("Calling external command:\n"); $cmd->hg("--version")->system; exit (0); It gives the following output when started via "env -i": $ which hg /usr/local/bin/hg $ env -i ./argv_test.pl Environment: Calling external command: + hg --version Mercurial Distributed SCM (version 1.9) (see http://mercurial.selenic.com for more information) Copyright (C) 2005-2011 Matt Mackall and others This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. + ($? == 0) How comes? Thanks... Dirk -- Dirk Heinrichs <dirk.heinrichs@altum.de> Tel: +49 (0)2471 209385 | Mobil: +49 (0)176 34473913 GPG Public Key C2E467BB | Jabber: dirk.heinrichs@altum.de

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Fri May 31 13:32:53 2013 dsb [...] cpan.org - Correspondence added

I don't have hg installed but I took your test program and replaced hg with git. It worked for me (meaning that it failed as expected). I do see that the error from exec is not shown, which may be a secondary bug, but that's orthogonal. Try the attached variant of your test case.

Subject:

rt85757-1.pl

#!/usr/bin/perl use strict; use warnings; use Argv; my $cmd=Argv->new({autochomp=>1,autofail=>1,dbglevel=>2}); # Verify internal environment is empty print ("Internal environment:\n"); foreach my $key ( sort( keys(%ENV) ) ) { printf( "%s=%s\n", $key, $ENV{$key} ); } # Compare external environment print ("External environment:\n"); $cmd->env->system; # Call external command print ("Calling external command:\n"); $cmd->git("--version")->system; exit (0);

Fri May 31 13:32:53 2013 The RT System itself - Status changed from 'new' to 'open'

Fri May 31 17:57:01 2013 dirk.heinrichs [...] altum.de - Correspondence added

Subject:	Re: [rt.cpan.org #85757] Argv finds external command even if environment is empty
Date:	Fri, 31 May 2013 23:56:32 +0200
To:	bug-Argv [...] rt.cpan.org
From:	Dirk Heinrichs <dirk.heinrichs [...] altum.de>

Hi, The result is the same, no matter where I try (RHEL 5.x, Debian Jessie (arm/i386), Ubuntu raring, Exherbo): % env -i ~/perl/argv_test.pl Internal environment: External environment: + env + ($? == 0) Calling external command: + git --version git version 1.8.3 + ($? == 0) $cmd->env->system; shouldn't work either, because env is an external command, and should be found via $PATH, which isn't set. I've also run it through strace, and I can clearly see that execve is searching some path (and that it has zero vars): 4430 execve("env", ["env"], [/* 0 vars */] <unfinished ...> 4429 wait4(4430, <unfinished ...> 4430 <... execve resumed> ) = -1 ENOENT (No such file or directory) 4430 execve("/bin/env", ["env"], [/* 0 vars */]) = 0 4431 execve("git", ["git", "--version"], [/* 0 vars */]) = -1 ENOENT (No such file or directory) 4431 execve("/bin/git", ["git", "--version"], [/* 0 vars */]) = -1 ENOENT (No such file or directory) 4431 execve("/usr/bin/git", ["git", "--version"], [/* 0 vars */]) = 0 But execve(3) doesn't mention any predefined path. Bye... Dirk -- Dirk Heinrichs <dirk.heinrichs@altum.de> Tel: +49 (0)2471 209385 | Mobil: +49 (0)176 34473913 GPG Public Key C2E467BB | Jabber: dirk.heinrichs@altum.de

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Fri May 31 18:56:33 2013 dsb [...] cpan.org - Correspondence added

I don't understand either, but it seems independent of Argv. This test case behaves identically for me on Ubuntu: #!/usr/bin/perl use strict; use warnings; system(qw(git --version)); exit (0);

Sat Jun 01 02:14:26 2013 dirk.heinrichs [...] altum.de - Correspondence added

Subject:	Re: [rt.cpan.org #85757] Argv finds external command even if environment is empty
Date:	Sat, 01 Jun 2013 08:14 +0200
To:	bug-Argv [...] rt.cpan.org
From:	Dirk Heinrichs <dirk.heinrichs [...] altum.de>

Ah, OK. I rarely use those functions directly, so I didn't recognize. I'll try to find an explanation elsewhere, then. Thank you very much for your effort. Bye... Dirk -- Dirk Heinrichs <dirk.heinrichs@altum.de> Tel: +49 (0)2471 209385 | Mobil: +49 (0)176 34473913 GPG Public Key C2E467BB | Jabber: dirk.heinrichs@altum.de

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