Is it possible to detect "no file" error in open2 ?

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

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Re: Is it possible to detect "no file" error in open2 ? by ikegami (Patriarch) on Dec 07, 2007 at 16:47 UTC
`open2` successfully created the child (`fork`), so it returned the child's PID. But the child process was unable to execute the desired command (`exec`), so it died, setting the child's error code to something non-zero. To check if the child is still running, use `kill(0, $pid)` or `waitpid($pid, WNOHANG)` (less portable?) or `eof($out)` (good indicator, but not always correct). `waitpid` returns a number which includes the child's error code. See `$?` for details. You should be calling `waitpid` when using `open2`/`open3` even if you don't care about the error code, or else you'll leave zombie processes behind.	[reply] [d/l] [select]
Re: Is it possible to detect "no file" error in open2 ? by zentara (Archbishop) on Dec 07, 2007 at 18:04 UTC
This dies with a message from the forked pid. Although the die message on the line gets lost. I can't seem to figure out why your script dosn't work? I did find if you put a print statement BEFORE your next open statement, your script will die at the right line. Without the print, it stays alive and tries the next open. ???? `#!/usr/bin/perl use warnings; use strict; use IPC::Open2; my $cmd = '/no/such/command'; my($out,$in); open2($out, $in, $cmd) \|\| die("I thought script should die here: $!"); print $in "the_string\n" \|\| die ("print die here no fork: $!"); open(my $pipe, "$cmd\|") \|\| die("But it dies only here: $!");` [download] It gives the error: open2: exec of /no/such/command failed at ./655683.pl line 10 I'm not really a human, but I play one on earth. Cogito ergo sum a bum	[reply] [d/l]
Re: Is it possible to detect "no file" error in open2 ? by Anonymous Monk on Dec 07, 2007 at 20:46 UTC
From the documentation: open2() returns the process ID of the child process. It doesn't return on failure: it just raises an exception matching "/^open2:/".However, "exec" failures in the child are not detected. You'll have to trap SIGPIPE yourself.	[reply]
Re: Is it possible to detect "no file" error in open2 ? by bdimych (Monk) on Dec 08, 2007 at 02:36 UTC
still not solved with open2/open3 IPC::Run and IPC::Run3 seems better. Useful comparision ikegami, Anonymous Monk, couldn't you provide examples --- All my old tests work well with the following code, so I've fixed on it `use IPC::Run3; ... eval {run3 [ 'cmd', 'without subshell', 'and with any complex params 1<>2()[]{*}' ], 'and/now/I/can', 'redirect/child/streams', 'from/to/my/files' }; retcode_full_test_copypasted_from_perldoc_f_system; if ($@) { die("run3 failed but retcode_full_test passed: $@") } ...` [download]	[reply] [d/l]


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