A continue or break from a subshell inside a loop no longer works.
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
ubuntu-docs (Ubuntu) |
Invalid
|
Undecided
|
Unassigned |
Bug Description
The following code works in bash on any number of Linux distros, including
CentOS 6.10 - 7.8 and Ubuntu 14.04 - 18.04.
#!/bin/bash
#
# Test for continue from subshell issue...
#
echo SHELL is $SHELL
for i in $(seq 5)
do
(
echo loop $i
if [[ $i == 2 ]] ; then
echo i = $i - continue
continue
fi
if [[ $i == 4 ]] ; then
echo i = $i - exit
exit 1
fi
echo Loop $i subshell end
)
rc=$?
echo Loop $i rc $rc
done
--
The output on all of those machines is:
SHELL is /bin/bash
loop 1
Loop 1 subshell end
Loop 1 rc 0
loop 2
i = 2 - continue
Loop 2 rc 0
loop 3
Loop 3 subshell end
Loop 3 rc 0
loop 4
i = 4 - exit
Loop 4 rc 1
loop 5
Loop 5 subshell end
Loop 5 rc 0
---
On a Ubuntu 20.04 machine:
SHELL is /bin/bash
loop 1
Loop 1 subshell end
Loop 1 rc 0
loop 2
i = 2 - continue
packages/
or `until' loop
Loop 2 subshell end
Loop 2 rc 0
loop 3
Loop 3 subshell end
Loop 3 rc 0
loop 4
i = 4 - exit
Loop 4 rc 1
loop 5
Loop 5 subshell end
Loop 5 rc 0
--
If I change the shebang to: #!/bin/sh
the behavior is the same as the first example - except - on our machines, we
specifically link /bin/sh to bash:
$ ls -l /bin/sh
lrwxrwxrwx 1 root root 9 May 12 22:04 /bin/sh -> /bin/bash
Which seems just... weird.
This behavior seems to have started after a recent update to Ubuntu 20.04.
I realize that the argument can be made the new behavior is more technically
correct, but using a subshell to isolate vars between loops can be very helpful
and the fact that this has worked until now is concerning.
This is not a bug about the Ubuntu Desktop Guide, so closing.
I would recommend you to show your observation at Ask Ubuntu. If you then conclude that it's a bug, please report it against the bash package.