How to Trap exit code from system calls

emjga1 has asked for the wisdom of the Perl Monks concerning the following question:

Dear Monks

The following snipet of code , works fine
But how can I trap the exit code of the program check_nrpe
Which could be 0 , 1 , 2 or 254

open(CMD, "/local/nagios/libexec/check_nrpe -H $host|") or dir $!;
@CMD=<CMD>;
close(CMD);
[download]

I think I should be using fork or waitpid
but not sure how ?.

Thanks

Matt

Comment on How to Trap exit code from system calls Download Code

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Re: How to Trap exit code from system calls by Abigail-II (Bishop) on Jan 21, 2004 at 16:10 UTC
How about RTFM? From `perldoc -f close`: `If the file handle came from a piped open "close" will additionally return false if one of the other system calls involved fails or if the program exits with non-zero status. (If the only problem was that the program exited non-zero $! will be set to 0.) Closing a pipe also waits for the pro- cess executing on the pipe to complete, in case you want to look at the output of the pipe after- wards, and implicitly puts the exit status value of that command into $?.` [download] Abigail	[reply] [d/l]
Re: How to Trap exit code from system calls by Fletch (Bishop) on Jan 21, 2004 at 16:12 UTC
If you read `perldoc -f open` carefully: Closing any piped filehandle causes the parent process to wait for the child to finish, and returns the status value in $?.	[reply] [d/l]
Re: How to Trap exit code from system calls by tcf22 (Priest) on Jan 21, 2004 at 15:59 UTC
You could always just use a `system` call. Below is what the docs say about checking exit values and such. `Because system() and backticks block SIGINT and SIGQUIT, killing the p +rogram they're running doesn't actually interrupt your program. @args = ("command", "arg1", "arg2"); system(@args) == 0 or die "system @args failed: $?" You can check all the failure possibilities by inspecting $? like this +: $exit_value = $? >> 8; $signal_num = $? & 127; $dumped_core = $? & 128;` [download] - Tom	[reply] [d/l] [select]
Re: Re: How to Trap exit code from system calls by emjga1 (Novice) on Jan 22, 2004 at 11:02 UTC
Tom Thanks , I had looked at $? but did not get the expected answers from it and asumed I was doing somthing wrong. But using `$exit_value = $? >> 8;` Does just the job. Thanks Matt	[reply] [d/l]
Re: How to Trap exit code from system calls by geektron (Curate) on Jan 21, 2004 at 16:00 UTC
`system()` will return zero on success or nonzero on failure. you can examine the return value in $?. `perldoc -f system` is your friend. :-)	[reply] [d/l] [select]