How can i get the return code of a killed process in unix?

0
votes

I have a bash script where i kill a running process by sending the SIGTERM signal to it's process ID. However, i want to know the return code of the process i just sent the signal.

Is that possible?

i cannot use 'wait' because the process to kill was not started from my script and i'm receiving "pid ##### is not a child of this shell"

I did some tests in a command line, in a console where the process was running, after i send the SIGTERM signal (from another console), i checked the exit code and it was 143. I want to kill the process from a different script and catch that number.

1
unixprocesskillsigterm
yes but i can't execute that in a console because both, the running process and the script where i'm sending the signal, are background processes – Mary Jane
given your constraints, its not possible. Only hope is to wrap the process in something that can capture its exit code into a file, or echoed to stdout/err. I'll be happy to be proved wrong. Good luck. – shellter
If you want to know the return code of a process, better not to kill it ... – jlliagre

1 Answers

3
votes

As shellter said, you cannot get the exit code of a process except using wait (or waitpid(), etc...) and you can only do that if you are its parent.

But even if you could, think about this:

When you send a process a SIGTERM, only one of three things can happen:

  • The process has not installed any signal handler for SIGTERM. In this case it dies immediately as a result of the signal. But in this case the exit code is uninteresting – you already know what it is. On most platforms it is 143 (128 + integer value of SIGTERM), indicating, unsurprisingly, that the process has died as a result of SIGTERM.

  • The process has configured SIGTERM to be ignored. In this case, nothing happens, the process does not die, and so there is no exit code to obtain anyway.

  • The process has installed a signal handler for SIGTERM. In this case, the handler is invoked. The handler might do anything at all: possibly nothing, possibly exit immediately, possibly carry out some cleanup operation and exit later, possibly something completely different. Even if the process does exit, that's only an indirect result of the signal, and it happens at a later time, so there is no exit code to obtain that comes directly from the delivery of the signal.