What purpose does using exec in docker entrypoint scripts serve?

Question

For example in the redis official image:

https://github.com/docker-library/redis/blob/master/2.8/docker-entrypoint.sh

#!/bin/bash
set -e

if [ \"$1\"         


        

Answer 1

Think of it as an optimization like tail recursion.

If running another program is the final act of the shell script, there's not much of a need to have the shell run the program in a new process and wait for it. Using exec, the shell process replaces itself with the program.

In either case, the exit value of the shell script will be identical¹. Whatever program originally called the shell script will see an exit value that is equal to the exit value of the exec`ed program (or 127 if the program cannot be found).

¹ modulo corner cases such as a program doing something different depending on the name of its parent.