Bash script: `exit 0` fails to exit

Question

So I have this Bash script: ``` #!/bin/bash PID=`ps -u ...` if [ "$PID" = "" ]; then echo $(date) Server off: not backing up exit else echo "say Server backup in 10 seconds..." >> fifo sleep 10 STARTTIME="$(date +%s)" echo nosave >> fifo echo savenow >> fifo tail -n 3 -f server.log | while read line do if echo $line | grep -q 'save complete'; then echo $(date) Backing up... OF="./backups/backup $(date +%Y-%m-%d\ %H:%M:%S).tar.gz" tar -czhf "$OF" data echo autosave >> fifo echo "$(date) Backup complete, resuming..." echo "done" exit 0 echo "done2" fi TIMEDIFF="$(($(date +%s)-STARTTIME))" if ((TIMEDIFF > 70)); then echo "Save took too long, canceling backup." exit 1 fi done fi ``` Basically, the server takes input from a fifo and outputs to server.log. The fifo is used to send stop/start commands to the server for autosaves. At the end, once it receives the message from the server that the server has completed a save, it tar's the data directory and starts saves again. It's at the `exit…

Accepted Answer

Here's a smaller, self contained example that exhibits the same behavior:

```
echo foo > file
tail -f file | while read; do exit; done
```

The problem is that since each part of the pipeline runs in a subshell, `exit` only exits the `while read` loop, not the entire script.

It will then hang until `tail` finds a new line, tries to write it, and discovers that the pipe is broken.

To fix it, you can replace

```
tail -n 3 -f server.log | while read line
    do
       ...
    done
```

with

```
while read line
do
   ...
done  <  <(tail -n 3 -f server.log)
```

By redirecting from a process substitution instead, the flow doesn't have to wait for `tail` to finish like it would in a pipeline, and it won't run in a subshell so that `exit` will actually exits the entire script.

Bash script: `exit 0` fails to exit

Solution

Problem