invoke shell with `` failed

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

Replies are listed 'Best First'.
Re: invoke shell with `` failed by almut (Canon) on Apr 15, 2009 at 10:35 UTC
Are you maybe leaving behind stuff in the environment upon every iteration? On most Unixes, the command line arguments share a fixed space with the process' environment. For example, the following would reproduce the issue (tested on Linux): #!/usr/bin/perl for (1..10) { $ENV{JUNK} .= "ABC" x 5000; my $begin_load = `cat /proc/loadavg`; warn "cat failed: $!" if $?; print $begin_load; } __END__ 0.56 0.43 0.25 1/219 27522 0.56 0.43 0.25 3/219 27523 0.56 0.43 0.25 2/219 27524 0.56 0.43 0.25 2/219 27525 0.56 0.43 0.25 2/219 27526 0.56 0.43 0.25 2/219 27527 0.56 0.43 0.25 3/219 27528 0.56 0.43 0.25 3/219 27529 cat failed: Argument list too long at ./757540.pl line 7. cat failed: Argument list too long at ./757540.pl line 7. [download]	[reply] [d/l]
Re^2: invoke shell with `` failed by jiangliguo (Initiate) on Apr 16, 2009 at 09:56 UTC
Really appreciate for your help,it should be the real reason. Is there any good method to avoid such situation since each iteration env is not the same.	[reply]
Re: invoke shell with `` failed by ikegami (Patriarch) on Apr 15, 2009 at 05:09 UTC
Like you were told multiple times in the CB, the shell never see $dir — it sees its content — so it's useless to say `df $dir` without telling us what `$dir` contains. It seems that it contains something that's either very long or something the shells expands into something very long.	[reply] [d/l] [select]
Re^2: invoke shell with `` failed by ikegami (Patriarch) on Apr 15, 2009 at 05:16 UTC
This doesn't excuse not telling us what `$dir` contains (or even rule it out), but it seems the error is coming from Perl code, not from the shell. That's most curious, and I'm wondering about a false positive. But since you didn't provide us the code that issues the error, can't tell.	[reply] [d/l]
Re^3: invoke shell with `` failed by jiangliguo (Initiate) on Apr 15, 2009 at 06:02 UTC
following is my script for space detect here the dir is: "/slowfs/hspice01/liguoj/performance/MT4/Rundir/Tue/RHEL4", and will not change during runtime. detect_disk() will invoke many times, the problem is during the first several times it run correct, but then failed. sub detect_disk { my ($flag, $dir) = @_; my $available_space = `df $dir`; my @array = split(/\s+/, $available_space); $available_space = $array[10]; if ($flag eq 'entry' and $available_space < 6000000) { print ("NOTICE: The left space of $dir is $available_space (KB +), please make sure enough space is available for the regresssion.\n\ +n"); } elsif ($flag eq 'routine' and ($available_space < 1000000)) { print ("NOTICE: The left space of $dir is $available_space (KB +), regression will waiting!\n"); sleep 60; while ($available_space < 1000000) { # send_mail($mail_list, $report_title, $report_file); $available_space = `df $dir`; @array = split(/\s+/, $available_space); $available_space = $array[10]; sleep 60; } } } [download]	[reply] [d/l]
Re^4: invoke shell with `` failed by Porculus (Hermit) on Apr 15, 2009 at 08:38 UTC
Re: invoke shell with `` failed by cdarke (Prior) on Apr 15, 2009 at 08:42 UTC
This is similar to node 684300. Depending on the version of *NIX you are using, there are limitations on the length or number of command line arguments, set in kernel. Some platforms have a limit of 255 entries, Linux has a size limit instead which defaults to (last time I looked) 32 pages (128kb on 32-bit Intel), but this can be changed by tweeking a kernel parameter. Check the number, and size, of parameters being sent in the command.	[reply]
Re^2: invoke shell with `` failed by jiangliguo (Initiate) on Apr 15, 2009 at 09:09 UTC
It seems my problem is not the same as node 684300. since when i use $begin_load = `cat /proc/loadavg`; [download] I will also encounter the same issue.	[reply] [d/l]
Re^3: invoke shell with `` failed by parv (Parson) on Apr 15, 2009 at 10:07 UTC
What about environment variables mentioned later, which did not occur to me at the time of my reply to perl: Argument list too long?	[reply]
Re^3: invoke shell with `` failed by pat_mc (Pilgrim) on Apr 15, 2009 at 10:01 UTC
Clearly, my $variable = `cat some.file`; [download] works fine for "well-behaved" files. I suspect the problem you are having is due to the contents of the file you are listing. Either it is too large (i.e. larger than your RAM so Perl cannot fit it into the scalar, which is unlikely) or it contains some character sequence that causes problems. Does your shell list the file OK? Cheers - Pat	[reply] [d/l]