Exit codes indicatesindicate a failure condition when ending a program and they,
and they fall between 0 0 and 255 255. The
The shell and its builtins may use especially the values above 125 to indicatespecially
to indicate specific failure modes, so list
so the list of codes can vary between shells and operating systems
(e.g., Bash uses the value 128+N128+N as the exit status). See
See: Bash - 3.7.5 Exit Status or man bash.
In general, a zero exit status indicates that a command succeeded,
and a non-zero exit status indicates failure.
To check which error code is returned by the command, you
you can print $? for the last exit code or ${PIPESTATUS[@]} which
which gives a list of exit status values from a pipeline (in Bash) after
after a shell script exits.
There is no full list of all exit codes which can be foundfound;
however, however there has been an attempt to systematize exit status numbers in kernel source, but.
But this is mainmainly intended for C/C++ programmers and similar,
and a similar standard for scripting might be appropriate.
The above list allocates previously unused exit codes from 64-78. The range
The range of unallottedunallocated exit codes will be further restricted in the future.
However above, the above values are mainly used in sendmail and used by pretty much nobody else, so they aren't anything remotely close to a standard (as pointed out by @GillesGilles).
In shell, the exit status values are as followfollows (based on Bash):
1-125 - Command did not complete successfully. Check
Check the command's man page for the meaning of the status, few.
A few examples below:
1 - Catchall for general errors
Miscellaneous errors, such as "divide by zero" and other impermissible operations.
Example:
$ let "var1 = 1/0"; echo $?
-bash: let: var1 = 1/0: division by 0 (error token is "0")
1
2 - Misuse of shell builtins (according to Bash documentation)
Missing keyword or command, or permission problem (and diff return code on a failed binary file comparison).
Example:
empty_function() {}
6 - No such device or address
Example:
$ curl foo; echo $?
curl: (6) Could not resolve host: foo
6
124 - command times out
125 - if a command itself failssee: coreutils (see: coreutils)
126 - if command is found but cannot be invoked (e.g., is not executable)
Permission problem or command is not an executable.
Example:
$ /dev/null
$ /etc/hosts; echo $?
-bash: /etc/hosts: Permission denied
126
127 - if a command cannot be found, the child process created to execute it returns that status
Possible problem with $PATH or a typo.
Example:
$ foo; echo $?
-bash: foo: command not found
127
128 - Invalid argument to exit
exit takes only integer args in the range 0 - 255.
Example:
$ exit 3.14159
-bash: exit: 3.14159: numeric argument required
128-254 - fatal error signal "n" - command died due to receiving a signal. The signal code is added to 128 (128 + SIGNAL) to get the status (Linux: man 7 signal, BSD: man signal), few examples below:
130 - command terminated due to Ctrl-C being pressed, 130-128=2 (SIGINT)
Example:
$ cat
^C
$ echo $?
130
137 - if command is sent the KILL(9) signal (128+9), the exit status of command otherwise
kill -9 $PPID of script.
141 - SIGPIPE - write on a pipe with no reader
Example:
$ hexdump -n100000 /dev/urandom | tee &>/dev/null >(cat > file1.txt) >(cat > file2.txt) >(cat > file3.txt) >(cat > file4.txt) >(cat > file5.txt)
$ find . -name '*.txt' -print0 | xargs -r0 cat | tee &>/dev/null >(head /dev/stdin > head.out) >(tail /dev/stdin > tail.out)
xargs: cat: terminated by signal 13
$ echo ${PIPESTATUS[@]}
0 125 141
143 - command terminated by signal code 15 (128+15=143)
Example:
$ sleep 5 && killall sleep &
[1] 19891
$ sleep 100; echo $?
Terminated: 15
143
255* - exit status out of range.
exit takes only integer args in the range 0 - 255.
Example:
$ sh -c 'exit 3.14159'; echo $?
sh: line 0: exit: 3.14159: numeric argument required
255
Please note that out of range exit values can result in unexpected exit codes (e.g. exit 3809, exit 3809 gives an exit code of 225, because 3809 % 256 = 225).
