Restarting program automatically on crash in OSX

Question

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How do I write a bash script to restart a process if it dies?

I've made a C program that occasionally crashes and I can't fix it (Some problem with getaddrinfo which is rather spontaneous seeming). I would like to restart the program upon the crash. I thought this would be easy. I was going to separate the problematic libcurl code with a fork and look up how I can detect a process from closing so it can be forked again. However I went with the "easy" option of trying to restart the entire program and recover data from a file.

I tried this:

#!/bin/sh
while true; do
    cd "~/ProgramDir"
    exec "~/ProgramDir/Program"
done

But when the program exits on a failure it starts outputting the next execution to the terminal input if that makes sense. SO if I pretend my program is just a Hello World program then it would do something like this:

bash-3.2$ start.sh
Hello World!
Hello World!
bus error
bash-3.2$ Hello World!
-bash: Hello: command not found
bash-3.2$ Hello World!
-bash: Hello: command not found

It wont continue the program as before. The terminal thinks the program has exited but then takes the output of the next execution to the terminal input.

What is the proper way to do this?

Are you sure you pasted your actual start script correctly (especially the quotes)? — Mat, Aug 30 '11 at 17:52
This is a really bad approach. Just find why your program is crashing and fix it. — R.. GitHub STOP HELPING ICE, Aug 30 '11 at 18:14

etuardu · Accepted Answer · 2012-09-28T17:41:18.293

8

#!/bin/bash

~/ProgramDir/Program || exec "$0"

This script would run "~/ProgramDir/Program" and wait for its exit status. If the status is 0 (which means "success" in bash), then the script itself terminates. Otherwise, if the program returns a non-0 value or it terminates unnaturally (e.g. it get killed), the script would launch itself again, like a tail recursion in C.

Edit: code updated according to R..'s comment

edited Sep 28 '12 at 17:41

answered Aug 30 '11 at 17:58

etuardu

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Make that `exec $0`. If you just use `$0`, it's recursion without tail recursion optimization, i.e. you'll get a new level of shell each time until you eventually run out of process ids/memory. – R.. GitHub STOP HELPING ICE Aug 30 '11 at 18:13
1

It works perfectly thankyou. exec "$0" works when there are spaces. – Matthew Mitchell Aug 30 '11 at 22:40

score 2 · Answer 2 · answered Aug 30 '11 at 17:59

When you use exec the shell will replace itself entirely with the program it starts. Unless the program fails even to load the first time around, there will be no shell left to continue the while loop after the program dies.

I'm not sure how this could produce the further behavior you describe, though.

Restarting program automatically on crash in OSX

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