This library is useful to aid in the readability of exit codes for APIs that use them. You can restrict your API to only use these codes, or if you are using an API that takes an Int for an exit code, you can make the code more explicit by deriving it via fromEnum:
> fromEnum Error
1
> fromEnum SIGKILL
137The exit codes follow the Bash and BSD standards. Here are some excerpts for reference (see the full text for complete details).
| Exit Code Number | Meaning | Example | Comments |
|---|---|---|---|
| 1 | Catchall for general errors | let "var1 = 1/0" | Miscellaneous errors, such as "divide by zero" and other impermissible operations |
| 2 | Misuse of shell builtins (according to Bash documentation) | empty_function() {} | Missing keyword or command, or permission problem (and diff return code on a failed binary file comparison). |
| 126 | Command invoked cannot execute | /dev/null | Permission problem or command is not an executable |
| 127 | "command not found" | illegal_command | Possible problem with $PATH or a typo |
| 128 | Invalid argument to exit | exit 3.14159 | exit takes only integer args in the range 0 - 255 (see first footnote) |
| 128+n | Fatal error signal "n" | kill -9 $PPID of script | $? returns 137 (128 + 9) |
| 130 | Script terminated by Control-C | Ctl-C | Control-C is fatal error signal 2, (130 = 128 + 2, see above) |
| 255* | Exit status out of range | exit -1 | exit takes only integer args in the range 0 - 255 |
| Signal | Value | Action | Comment |
|---|---|---|---|
| SIGHUP | 1 | Term | Hangup detected on controlling terminal or death of controlling process |
| SIGINT | 2 | Term | Interrupt from keyboard |
| SIGQUIT | 3 | Core | Quit from keyboard |
| SIGILL | 4 | Core | Illegal Instruction |
| SIGABRT | 6 | Core | Abort signal from abort(3) |
| SIGFPE | 8 | Core | Floating point exception |
| SIGKILL | 9 | Term | Kill signal |
| SIGSEGV | 11 | Core | Invalid memory reference |
| SIGPIPE | 13 | Term | Broken pipe: write to pipe with no readers |
| SIGALRM | 14 | Term | Timer signal from alarm(2) |
| SIGTERM | 15 | Term | Termination signal |
#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 */