How do I set a ulimit from inside a Perl script that applies to its children?
I have a Perl script that does various installation steps to set up a development box for our company. It runs various shell scripts, some of which crash due to lower than required ulimit
s (specifically, stack size -s
in my case).
Therefore, I'd like to set a ulimit
that would apply to all scripts (children
) started from within my main Perl one, but I am not sure how to achieve that - any attempts at calling ulimit from within the script only set it on that specific child shell, which immediately exits.
I am aware that I can call ulimit
before I run the Perl script or use /etc/security/limits.conf
but I don't want the user to know any of this - they should only know how to run the script, which should take care of all of that for them.
I can also run ulimit
every time I run a command, like this ulimit -s BLA; ./cmd
but I don't want to duplicate this every time and I feel like there's a better, cleaner solution out there.
Another crazy "workaround" is to make a wrapper script called BLA.sh which would set ulimit and call BLA.pl, but again, it's a hack in my mind and now I'd have 2 scripts (I could even make BLA.pl call itself with "ulimit -s BLA; ./BLA.pl --foo" and act differently based 开发者_JAVA百科on whether it sees --foo or not but that's even hackier than before).
Finally, apparently I could install BSD::Resource but I'd like to avoid using external dependencies.
So what is THE way to set the ulimit from within a Perl script and make it apply to all children?
Thank you.
You've already answered your question: use BSD::Resource.
There isn't anything in the Perl core that interfaces with setrlimit
. If you can't (or won't) use the standard method, then you have to use a hack. Any of the methods you've already described would work. (Note that you could create a subroutine to prepend ulimit -s BLA;
to every command, and then use that sub instead of system
.)
Here's an example of how to set the cpu limit without using BSD::Resource (but assuming the perl system headers are there). To adapt to other resources, make the obvious changes.
require 'syscall.ph';
require 'sys/resource.ph';
# set the soft cpu limit to 1 (second), and the hard limit to 10.
$rstruct = pack "L!L!",1,10; # L! means native long unsigned int.
syscall(&SYS_setrlimit,&RLIMIT_CPU,$rstruct);
This assumes knowledge that rlim_t is in fact unsigned long; I don't know if there's a way to extract this info from the Perl headers.
You can always wrap your perl in a little shell script:
#!/bin/sh -- # --*-Perl-*--
ulimit -n 2048
exec /usr/bin/perl -x -S $0 ${1+"$@"}
#!/usr/bin/perl
#line 6
use strict;
# etc, etc....
It's ugly, and obviously, script start up time will be slightly longer.
I ended up prepending ulimit -s BLA
to the commands that needed it. I specifically didn't want to go with BSD::Resource because it's not a default Perl package and was missing on about half of the existing dev machines. No user interaction was a specific requirement.
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