Are there any standard exit status codes in Linux?

Question

A process is considered to have completed correctly in Linux if its exit status was 0.

I've seen that segmentation faults often result in an exit status of 11, though I don't know if this is simply the convention where I work (the applications that failed like that have all been internal) or a standard.

Are there standard exit codes for processes in Linux?

Answer 1

8 bits of the return code and 8 bits of the number of the killing signal are mixed into a single value on the return from wait(2) & co..

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <signal.h>

int main() {
    int status;

    pid_t child = fork();
    if (child <= 0)
        exit(42);
    waitpid(child, &status, 0);
    if (WIFEXITED(status))
        printf("first child exited with %u\n", WEXITSTATUS(status));
    /* prints: "first child exited with 42" */

    child = fork();
    if (child <= 0)
        kill(getpid(), SIGSEGV);
    waitpid(child, &status, 0);
    if (WIFSIGNALED(status))
        printf("second child died with %u\n", WTERMSIG(status));
    /* prints: "second child died with 11" */
}

How are you determining the exit status? Traditionally, the shell only stores an 8-bit return code, but sets the high bit if the process was abnormally terminated.

$ sh -c 'exit 42'; echo $?
42
$ sh -c 'kill -SEGV $$'; echo $?
Segmentation fault
139
$ expr 139 - 128
11

If you're seeing anything other than this, then the program probably has a SIGSEGV signal handler which then calls exit normally, so it isn't actually getting killed by the signal. (Programs can chose to handle any signals aside from SIGKILL and SIGSTOP.)