Change application core dump directory with c program - c

Question

I have one scenario where I want to change directory for core dumps by current application using c program.
I have one option to do chdir() to specified directory. But this changes the home directory of application. And I am looking for some APIs which can change directory for core dumps only.

Answer 1

You can change core dump pattern globally through /proc/sys/kernel/core_pattern.
But if you only want to change the core dump directory of one process, you can do what Apache web server does - register a signal handler that changes the current directory right before core dumping:
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <sys/resource.h>
#define COREDUMP_DIR "/tmp"
static void sig_coredump (int sig)
{
struct sigaction sa;
// Change to the directory we want the core to be dumped
chdir (COREDUMP_DIR);
// Clear the signal handler for the signal
memset (&sa, 0, sizeof (sa));
sa.sa_handler = SIG_DFL;
sigemptyset (&sa.sa_mask);
sigaction (sig, &sa, NULL);
// Send the signal again
raise (sig);
}
int main (int argc, char **argv)
{
struct sigaction sa;
// Set up the signal handler for all signals that
// can cause the core dump
memset (&sa, 0, sizeof (sa));
sa.sa_handler = sig_coredump;
sigemptyset (&sa.sa_mask);
sigaction (SIGSEGV, &sa, NULL);
sigaction (SIGBUS, &sa, NULL);
sigaction (SIGABRT, &sa, NULL);
sigaction (SIGILL, &sa, NULL);
sigaction (SIGFPE, &sa, NULL);
// Enable core dump
struct rlimit core_limit;
core_limit.rlim_cur = RLIM_INFINITY;
core_limit.rlim_max = RLIM_INFINITY;
if (setrlimit (RLIMIT_CORE, &core_limit) == -1) {
perror ("setrlimit");
}
// Trigger core dump
raise (SIGSEGV);
return 0;
}
Note that as this relies on the crashing application itself setting up and being able to run the signal handler, it can't be 100% bullet-proof - signal may be delivered before signal handler is set up or signal handling itself may get corrupted.