Re: need explanation ulimit -c for limiting core dumps

[Jason Roscoe]

Chet Ramey wrote:
> Matthew Woehlke wrote:
> > Chet Ramey wrote:
> > > jason.roscoe@gmail.com wrote:
> > > > I'm trying to limit the size of coredumps using 'ulimit -c'.  Can
> > > someone please explain why a core file gets generated from the coretest
> > > program (source is below)?
> > > > Thanks for any help or suggestions.
> > > >
> > > > % ulimit -H -c
> > > > 512
> > > > % ./coretest 2048
> > > > rlim_cur,rlim_max = 524288,524288
> > > > malloced 2097152 bytes my pid is 21255
> > > > Segmentation fault (core dumped)
> > > > % ls -l core
> > > > -rw-------  1 jacr swdvt 2265088 2006-10-19 14:24 core
> > > Are you sure that's not an old core file?  My Linux testing indicates
> > > that
> > > the coredump bit is set in the exit status, but no core file is actually
> > > created:
> > >
> > > $ ulimit -c 512
> > > $ ./xcore 2048
> > > rlim_cur,rlim_max = 524288,524288
> > > malloced 2097152 bytes my pid is 7661
> > > Segmentation fault (core dumped)
> > > $ ls -ls core
> > > /bin/ls: core: No such file or directory
> > You sure your Linux makes 'core' and not 'core.<pid>', right? You might
> > want to do 'ls -ls core*' instead...
>
> You are correct.  Man, I'm having a bad day.  The sparse core file
> has fewer blocks than the limit, though, so it's not truncated.
>
> Chet

Thanks for the help folks.  Not sure if you knew this or not, but at 
least on my linux boxen you can use '# sysctl kernel.core_pattern' to 
see where core files will be created and their name.  I guess it's 
typically kernel.core_pattern = core, but sometimes you'll find 
kernel.core_pattern = core.%p to add the PID on the end of the name.

Jason