The program below can be used to demonstrate the use of the pipe
syntax in the /proc/sys/kernel/core_pattern file. The following
shell session demonstrates the use of this program (compiled to
create an executable named core_pattern_pipe_test):
$ cc -o core_pattern_pipe_test core_pattern_pipe_test.c
$ su
Password:
# echo "|$PWD/core_pattern_pipe_test %p UID=%u GID=%g sig=%s" > \
/proc/sys/kernel/core_pattern
# exit
$ sleep 100
^\ # type control-backslash
Quit (core dumped)
$ cat core.info
argc=5
argc[0]=</home/mtk/core_pattern_pipe_test>
argc[1]=<20575>
argc[2]=<UID=1000>
argc[3]=<GID=100>
argc[4]=<sig=3>
Total bytes in core dump: 282624
Program source
/* core_pattern_pipe_test.c */
#define _GNU_SOURCE
#include <sys/stat.h>
#include <fcntl.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#define BUF_SIZE 1024
int
main(int argc, char *argv[])
{
ssize_t nread, tot;
char buf[BUF_SIZE];
FILE *fp;
char cwd[PATH_MAX];
/* Change our current working directory to that of the
crashing process. */
snprintf(cwd, PATH_MAX, "/proc/%s/cwd", argv[1]);
chdir(cwd);
/* Write output to file "core.info" in that directory. */
fp = fopen("core.info", "w+");
if (fp == NULL)
exit(EXIT_FAILURE);
/* Display command-line arguments given to core_pattern
pipe program. */
fprintf(fp, "argc=%d\n", argc);
for (int j = 0; j < argc; j++)
fprintf(fp, "argc[%d]=<%s>\n", j, argv[j]);
/* Count bytes in standard input (the core dump). */
tot = 0;
while ((nread = read(STDIN_FILENO, buf, BUF_SIZE)) > 0)
tot += nread;
fprintf(fp, "Total bytes in core dump: %zd\n", tot);
fclose(fp);
exit(EXIT_SUCCESS);
}
