commands/gcore/gcore.c
/* gcore - create core file of running process */

#include <sys/types.h>
#include <sys/ptrace.h>
#include <sys/wait.h>
#include <signal.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int main(int argc, char *argv[])
{
  pid_t pid;
  int status;

  if(argc != 2) {
	printf("usage: %s <pid>\n", argv[0]);
	return 1;
  }

  pid = atoi(argv[1]);

  if (ptrace(T_ATTACH, pid, 0, 0) != 0) {
	perror("ptrace(T_ATTACH)");
	return 1;
  }

  if (waitpid(pid, &status, 0) != pid) {
	perror("waitpid");
	return 1;
  }

  while (WIFSTOPPED(status) && WSTOPSIG(status) != SIGSTOP) {
	/* whatever happens here is fine */
	ptrace(T_RESUME, pid, 0, WSTOPSIG(status));

	if (waitpid(pid, &status, 0) != pid) {
		perror("waitpid");
		return 1;
	}
  }

  if (!WIFSTOPPED(status)) {
	fprintf(stderr, "process died while attaching\n");
	return 1;
  }

  if (ptrace(T_DUMPCORE, pid, 0, 0)) {
	fprintf(stderr, "warning, dumpcore failed (%s)\n", strerror(errno));
  }

  if (ptrace(T_DETACH, pid, 0, 0)) {
	fprintf(stderr, "warning, detaching failed (%s)\n", strerror(errno));
  }

  return 0;
}
