bash_fail-to-wait

ℹ️ This is fixed in Bash-5.1 patch 10.

Small repository used to reproduce a potential bug with the wait command in Bash >=5.1.0

The Problem

The wait command cannot be called again after it has been interrupted by a system signal (e.g. SIGHUP), and exits with code 127.

This is not the case in Bash 5.0.x, so I would say this is a regression of some sort.

What Is Happening

In the fail_to_wait.sh I create a trap for SIGHUP which only prints that a signal of this type has been received. Sending in such a signal will cause the wait at the bottom to return (this is expected), but since we still want to wait for our child process we loop and wait again in the case that the exit code was 128+SIGHUP=129.

In Bash 5.0.3 this works as expected, and the script will return to waiting for the child process to exit. However, in Bash 5.1.0 we get an error from wait and it exits with code 127 the second time we try to wait for the child process.

My real world usage of this feature can be found here.

How to Reproduce

To make it simple to reproduce I have created a Docker image and a Makefile that have all the necessary commands listed. Do it in the following order to reproduce:

make build

make run50

and from another terminal you can send in a SIGHUP via the following command:

make send-sighup

Since we are running Bash 5.0 this should not produce an error. Close the container by giving it Ctrl+C, and then starting the same script again but using Bash 5.1 this time:

make run51

Sending in the signal this time should terminate the container with exit code 127.