APM: Question: How to access command line before its parsed into @ARGV

[Wayne Walker]

Bill, and all APM folks,

The guys that wrote the original shells were very smart.  While perl can
probably solve Bill's problem, the shell can probably solve it in 5
lines.  (--noprofile is a bash/sh thing on linux; find the equivalent
thing in AIX's /bin/sh, I've no AIX box to check).

This should do everything you need:

mv miscreant miscreant.real
touch miscreant
chmod 755 miscreant
vim miscreant  (emacs might work, by why take chances??  :)
----------------------------------
#!/bin/sh --noprofile

# Store the environment for later perusal
env > /tmp/env.$$

# Read stdin and store it for later perusal
cat > /tmp/stdin.$$

# The "'s around $@ are critical (man sh, then search for \$\@ or $@
# according to what pager you are using
# run the real miscreant saving stdout and sterr
$0.real "$@" < /tmp/stdin.$$ > /tmp/stdout.$$ 2> /tmp/stderr.$$

# feed stdout and stderr to whatever called miscreant
cat /tmp/stdout.$$
cat /tmp/stderr.$$ 1>&2
----------------------------------

$@ will expand in a way that recreates quoting with functional exactness
(something that didn't have/need quotes will get quoted, but the shell
will rip them back off such that it will exactly mimic the original
calling).

This will only not work if there is a time sensitive issue with the
interleaving of stdout and stderr.  That is a rare situation, but I
have seen it.

Wayne

On Thu, Aug 25, 2005 at 03:23:59PM -0700, Bill Raty wrote:
> Folks,
> 
> In Linux one can access the pre-parsed command line given to
> exec, using CPAN module Proc::ProcessTable .   It seems to
> reflect the assertions that quotes are removed by the shell
> before being given to exec.
> 
> =for example
> 
> use strict;
> use warnings;
> use Proc::ProcessTable;
> 
> my $proc_table = Proc::ProcessTable->new();
> my ($process) = grep $_->{pid} == $$, @{ $proc_table->table()
> };
> my $cmndline = $process->{cmndline};
> print "Command line for pid=$$: ($cmndline)\n";
> 
> =cut
> 
> The underlying problem is I need to gather forensics on an
> executable running on AIX that hangs intermittently.  The idea
> was to put a command proxy in its place (perl) that captures
> invocation arguments, STDIN, invokes the miscreant, and logs
> its STDOUT, STDERR and other vitals for later analysis. 
> Hopefully I'll be able to gather information for logging a
> support ticket with the producer of the executable.
> 
> Presumably the quotes I supply to this program don't reach it,
> and I can apply the cmndline from above to an 'exec', 'open',
> or 'open3'.
> 
> 
> 
> -Bill
> Reintarnation: Coming back to life as a hillbilly
> 
> _______________________________________________
> Austin mailing list
> Austin at pm.org
> http://mail.pm.org/mailman/listinfo/austin

-- 

Wayne Walker

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