exit code when crashed

问题:

I like to know whether application is crashed or not from shell script. What would be the exit code if application crashed?

回答1:

The exit code of the application will be in the shell variable $?. If your application crashes, i.e. the operating system decides it has done something bad, and causes it to terminate (sends it a signal), then this is reflected in exit status $?.

Here is a simple function I use (in bash I set it as the PROMPT_COMMAND variable) put does some decoding of the exit status

check_exit_status () 
{ 
    local status="$?";
    local msg="";
    local signal="";
    if [ ${status} -ne 0 ]; then
        if [ $((${status} < 128)) -ne 0 ]; then
            msg="exit (${status})";
        else
            signal="$(builtin kill -l $((${status} - 128)) 2>/dev/null)";
            if [ "$signal" ]; then
                msg="kill -$signal$msg";
            fi;
        fi;
        echo "[${status} => ${msg}]" 1>&2;
    fi;
    return 0
}

Hope you find it useful.

回答2:

Anything other than 0 indicates an error. Error values range from 1-255. Check them with $?.

There are some exceptions to this, but 0 for success is the de facto standard on *nix.

回答3:

Normally the return code is 0 when nothing went wrong. You can check the return code with $?

  fab@susi:~$ badCommand  
  badCommand: command not found  
  fab@susi:~$   
  fab@susi:~$ echo $?  
  127  
  fab@susi:~$   
  fab@susi:~$ whoami  
  fab  
  fab@susi:~$   
  fab@susi:~$ echo $?  
  0  
  fab@susi:~$

回答4:

Seems this is an answer to your question. The code snippet there demonstrates that the answer depends on the operating system (including Windows).