Exit codes

An Exit Code or Exit Status is an unsigned 8-bit integer returned by a command that indicates how its execution went.

 

An Exit Code of 0 indicates the command (program) was successful at what it was supposed to do. I think of it as zero means the program exited successfully with zero errors.

 

Any other Exit Code indicates that something went wrong.

 

Applications can choose for themselves what number indicates what went wrong; so refer to the manual of the application to find out what the application's Exit Code means.

 

The $? shell parameter provides the exit status (/ return value) of the most recently executed foreground pipeline.

 

echo $?

 

#!/bin/bash

#here's a command that will fail
mv-l
#just so we can see it's exit code:
echo $?

 

 

Developers are free to specify their own exit codes, but must not interfere with the Reserved Exit Codes:

 

Exit Code Number Meaning
0 Success
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"
130 Script terminated by Control-C
255* Exit status out of range

 

Exit codes can be viewed using echo $?