On Thu, May 16, 2002 at 05:24:47PM +0100, Jonathan E. Paton wrote:
>
> ln -s /dev/null core
I thought you deserved a beating...
> just stick into any directory where you could
> have a core dump. You must be doing something
> mission critical to be desperate to stop these,
> but not mission critical enough to want to use
> them.
....until I read this previous paragraph. Phew! ;-)
> Why not just get cron to recurse over your
> directories eliminating core files when the
> filesystem gets a little cramped?
In that case I'd recommend above solution as the lesser evil since it
gives you at least a bit control over which cores to see and which not.
Well, a *nice* daemon would chdir to '/' anyways, so putting that
symlink there would be the same as traversing the tree and clobbering
each and every coredump one can find, which again sucks.
> I know it is dumb, but why not just wrap your
> perl script in one of these coredump eliminating
> shell scripts - the child processes will get
> those properties.
Or set the limit to disallow cores inside the shellscript.
> Oh, and Perl probably does have a way of doing
> this... try POSIX.pm, or the syscall function
> (you'll need to know what to look for, ask a
> C programmer how they do it).
Nope, it's not in POSIX as far as I know.
Hmm, never used syscall... Let's harvest some information:
---------- perldoc -f syscall ----------
syscall LIST
...
The arguments are interpreted as follows: if a given argument is
numeric, the argument is passed as an int. If not, the pointer to
the string value is passed. You are responsible to make sure a
string is pre- extended long enough to receive any result that might
be written into a string.
...
require 'syscall.ph'; # may need to run h2ph
$s = "hi there\n";
syscall(&SYS_write, fileno(STDOUT), $s, length $s);
---------- perldoc -f syscall ----------
Hmmmm, looks easy enough...
---------- man getrlimit ----------
...
int getrlimit(int resource, struct rlimit *rlim);
...
getrlimit and setrlimit get and set resource limits respectively. resource should
be one of:
RLIMIT_CPU /* CPU time in seconds */
RLIMIT_FSIZE /* Maximum filesize */
RLIMIT_DATA /* max data size */
RLIMIT_STACK /* max stack size */
RLIMIT_CORE /* max core file size */
RLIMIT_RSS /* max resident set size */
RLIMIT_NPROC /* max number of processes */
RLIMIT_NOFILE /* max number of open files */
RLIMIT_MEMLOCK /* max locked-in-memory address space*/
RLIMIT_AS /* address space (virtual memory) limit */
...
The rlimit structure is defined as follows :
struct rlimit {
rlim_t rlim_cur;
rlim_t rlim_max;
};
...
RETURN VALUE
On success, zero is returned. On error, -1 is returned,
and errno is set appropriately.
---------- man getrlimit ----------
That should get us started...
---------- snip ----------
nijushiho:~$ grep RLIMIT_CORE /usr/include/*/* 2>/dev/null
/usr/include/asm/resource.h:#define RLIMIT_CORE 4 /* max core file
size */
/usr/include/bits/resource.h: RLIMIT_CORE = 4,
/usr/include/bits/resource.h:#define RLIMIT_CORE RLIMIT_CORE
---------- snip ----------
Aha, RLIMIT_CORE is 4...
---------- snip lim.pl ----------
#!/usr/bin/perl
use warnings;
use strict;
my $lim = pack('LL', 0, 0); # Yepp, I grepped some more in /usr/include/*
# to find out the sice of rlim_t
print "Failed: $!\n"
if syscall(&SYS_getrlimit(4, $lim)) < 0;
my ($cur, $max) = unpack('LL', $lim);
print "CUR: $cur\n";
print "MAX: $max\n";
---------- snip lim.pl ----------
Let's start it...
---------- snip ----------
nijushiho:~$ perl lim.pl
Returned Invalid argument
CUR: 0
MAX: 0
nijushiho:~$
---------- snip ----------
Hmmmm, what's up here?!? Anybody any ideas?
--
If we fail, we will lose the war.
Michael Lamertz | +49 221 445420 / +49 171 6900 310
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