Bash if else then in one line with bash version of sys.exit()

Question

I am running this bash command:

xe pbd-unplug uuid=$PBDUUID

If the result exists - i.e. if the variable

PBDUUID

is not empty then I would like to run another command:

xe sr-forget uuid=$SRUUID

However, if the variable is blank then I would like print an error message

Error: No PBD.

and for the script to exit immediately (similar to

sys.exit()

in Python).

Is there a way to combine this

if else then

into one line? Also, what is the bash equivalent of

sys.exit()

?

Additional Information/Comment:

Regarding comment by Dilettant, yes that approach (

if [ -z ${PBDUUID} ]; then

) will also work. I was not aware of it. Thanks for this. That seems quite intuitive.

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Answer 1

if xe pbd-unplug uuid="$PBDUUID"; then xe sr-forget "uuid=$SRUUID"; else echo "Error: No PBD."; exit 1; fi

More readably, that is:

if xe pbd-unplug uuid="$PBDUUID"; then
  xe sr-forget "uuid=$SRUUID"
else
  echo "Error: No PBD." >&2
  exit 1
fi

BTW, if your goal is to check whether a variable is blank, that would look more like the following:

if [ -z "$PDBUUID" ]; then
  xe pdb-unplug uuid="$PDBUUID" && xe sr-forget "uuid=$SRUUID"
else
  echo "Error: No PBD." >&2
  exit 1
fi

If exit doesn't do as you intend, then this code is presumably running in a subshell, and thus exit is exiting that subshell rather than your script as a whole. See SubShell or the "Actions that Create a Subshell" section of the processtree bash-hackers.org page.

Bash if else then in one line with bash version of sys.exit()

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