[PLUG] fun with perl: eval{} and exceptions

[sean finney <seanius@seanius.net>]

hey guys,

over the past couple days i've thrown together a nifty little perl
script to make a sysadmin's email-reading life a little easier.  it's
a wrapper to use around cron/at jobs that basically runs a process,
captures the stdin/stdout/exit, and reports what you care about via
email with a quick to grok subject header.  after i get this part
fully functional, i'll probably even add in regular expressions to
watch for.

anyway, it works reasonably well already, but i'm having trouble
with catching exceptions when the call to exec (via IPC::Open3)
fails due to a bad path/interpreter.  i'm doing something like

...
eval { $cmd_pid=open3(\*IN, \*OUT, \*ERR, @cmd); };
if($@ =~ /exec/){
	print "\@ is $@\n";
	$cmd_errstr = $@;
	$cmd_retval = "-1";
	die;
};
...
# code that sends email in if/else blocks


if i call the script with a command that doesn't exist, calling process
seems to fork, and i get two seperate emails--even though each part
of the code that sends the email is in a seperate block of an
if/elsif/else statement!  

furthermore, the file descriptors seem to get messed up and when the
command fails, the stdout/stderr of @cmd get mixed up with the
stdout/stderr of the calling process.  i think i have this one figured
out (descriptors not initialized having default values == STDIN/STDOUT)
but i'm not sure.

anyway, i realize this is a bit OT (yeah, yeah, i should be posting to
some perl-users list), but i promise to share the script with anyone
who might think it useful it when i'm done.  

in the meantime i think i'm just going to come up with some kind of hack
that just tries to stat() the file...


thanks,
	sean

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