Bash Script - umount a device, but don't fail if it's not mounted?
Question
I'm writing a bash script and I have errexit
set, so that the script will die if any command doesn't return a 0 exit code, i.e. if any command doesn't complete successfully. This is to make sure that my bash script is robust.
I have to mount some filesystems, copy some files over, the umount it. I'm putting a umount /mnt/temp
at the start so that it'll umount it before doing anything. However if it's not mounted then umount will fail and stop my script.
Is it possible to do a umount --dont-fail-if-not-mounted /mnt/temp
? So that it will return 0 if the device isn't mounted? Like rm -f
?
Solution
The standard trick to ignore the return code is to wrap the command in a boolean expression that always evaluates to success:
umount .... || /bin/true
OTHER TIPS
Assuming that your umount
returns 1 when device isn't mounted, you can do it like that:
umount … || [ $? -eq 1 ]
Then bash will assume no error if umount
returns 0 or 1 (i.e. unmounts successfully or device isn't mounted) but will stop the script if any other code is returned (e.g. you have no permissions to unmount the device).
I just found the ":" more use ful and wanted a similar solution but let the script know whats happening.
umount ...... || { echo "umount failed but not to worry" ; : ; }
This returns true with the message, though the umount failed.