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--- bash:command_exit_status [2019/12/11 00:17] – created peter
+++ bash:command_exit_status [2021/01/26 16:55] (current) – removed peter
@@ Line 1: / Line 1: @@
-====== BASH - Command Exit Status ======
-An exit status is an integer between 0 and 255 returned when a program exits.
-Usually readable by running
-<code bash>
-echo $?
-</code>
-This is in effect one of the key pieces of the API which shells use to communicate with the programs that they run.
-----
-In Bash-like shells, status 0 signals success and that status 1 is an error.
-A misuse of the program can either be signaled by 1 (as demonstrated by many programs including git or ls), or possibly a 2, which signals the misuse of a shell built-in.
-When a program receives a fatal signal, it will exit with a code of 128 + n where n is the signal code.
-For example, for a program sent signal 2 (SIGINT, or more commonly thought of as Ctrl+C):
-<code bash
-curl -n https://api.heroku.com/apps
-^C
-echo $?
-</code>
-The Advanced Bash-script Guide lists a number of other [[http://tldp.org/LDP/abs/html/exitcodes.html|reserved exit codes]].
-Some attempt at standardization has also been made in the kernel header sysexits.h:
-<file bash  /usr/include/sysexits.h>
-#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 */
-</file>