mjhjmtu

I want to suppress errors in my sub-shell after a certain point.

I wrote script to demonstrate the situation:

worked=false
(echo Starting subshell process 
 && echo If this executes process is considered success 
 && false 
 && echo run if possible, but not an error if failed) 
 && worked=true

echo $worked

I want to report back to the outer shell that the process worked.

I also thought about putting the worked variable inside the subshell:

 && echo This works process worked: 
 && worked=true 
 && false 
 && echo run if possible, but not an error if failed)

But this doesn't work either because setting a variable inside the subshell doesn't effect the main script.

How about this

worked=false
(
 set -e
 echo Starting subshell process
 echo If this executes process is considered success
 false
 echo run if possible, but not an error if failed || true
)
[[ 0 -eq $? ]] && worked=true

echo "$worked"

The set -e terminates the subshell as soon as an unprotected error is found. The || true construct protects a statement that might fail, where you don't want the subshell to terminate.

If you just want to know if the subshell succeeded you can dispense with the $worked variable entirely

(
 set -e
 ...
)
if [[ 0 -eq $? ]]
then
 echo "Success"
fi

Note that if you want to use set -e to abort execution in the subshell as soon as a command fails, you cannot use a construct such as ( set -e; ... ) && worked=true or if ( set -e; ...); then ... fi. This is documented in the man page for bash but I missed it first time round:

If a compound command or shell function sets -e while executing in a context where -e is ignored, that setting will not have any effect until the compound command or the command containing the function call completes.

worked=false
(status=1;
 echo Starting subshell process 
 && echo If this executes process is considered success 
 && status=0
 && false 
 && echo run if possible, but not an error if failed;
 exit $status) 
 && worked=true

echo $worked

You could put the mandatory commands in the condition of an if, no need to connect everything with a && chain:

worked=false
( if echo Starting subshell process &&
 echo If this executes process is considered success ; then
 false &&
 echo run if possible, but not an error if failed
 exit 0
 fi
 exit 1 ) && worked=true

echo worked=$worked

My solution was to create a variable inside the subshell and manually control the exit codes based on that:

worked=false
(echo Starting subshell process 
 && echo If this executes process is considered success 
 && check=true 
 && false 
 && echo run if possible, but not an error if failed
 if [[ -n "$check" ]]; then exit 0; else exit 1; fi) 
 && worked=true

echo $worked