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 apps that failed like that have all been internal) or a standard.

Are there standard exit codes for processes in Linux?

Answer 1

Part 1: Advanced Bash Scripting Guide

As always, the Advanced Bash Scripting Guide has great information: (This was linked in another answer, but to a non-canonical URL.)

1: Catchall for general errors
2: Misuse of shell builtins (according to Bash documentation)
126: Command invoked cannot execute
127: "command not found"
128: Invalid argument to exit
128+n: Fatal error signal "n"
255: Exit status out of range (exit takes only integer args in the range 0 - 255)

Part 2: sysexits.h

The ABSG references sysexits.h.

On Linux:

$ find /usr -name sysexits.h /usr/include/sysexits.h $ cat /usr/include/sysexits.h  /*  * Copyright (c) 1987, 1993  *  The Regents of the University of California.  All rights reserved.   (A whole bunch of text left out.)  #define EX_OK           0       /* successful termination */ #define EX__BASE        64      /* base value for error messages */ #define EX_USAGE        64      /* command line usage error */ #define EX_DATAERR      65      /* data format error */ #define EX_NOINPUT      66      /* cannot open input */     #define EX_NOUSER       67      /* addressee unknown */     #define EX_NOHOST       68      /* host name unknown */ #define EX_UNAVAILABLE  69      /* service unavailable */ #define EX_SOFTWARE     70      /* internal software error */ #define EX_OSERR        71      /* system error (e.g., can't fork) */ #define EX_OSFILE       72      /* critical OS file missing */ #define EX_CANTCREAT    73      /* can't create (user) output file */ #define EX_IOERR        74      /* input/output error */ #define EX_TEMPFAIL     75      /* temp failure; user is invited to retry */ #define EX_PROTOCOL     76      /* remote error in protocol */ #define EX_NOPERM       77      /* permission denied */ #define EX_CONFIG       78      /* configuration error */  #define EX__MAX 78      /* maximum listed value */ 

Answer 2

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.)