Exit command

See Exit in the commands.

Success

exit
# Same as
exit 0

Error

exit 1

Force success

The entire script will exit with the status of the last command, so you can force a success like this.

  • script.sh 
      false

  exit 0

This will always return a success.

$ bash script.sh

Get exit status

$?

e.g.

$ true
$ echo $?
0

$ false
$ echo $?
1

If you use assignment, the status is retained.

X=$(false)
echo $?
1

Or in one line:

$ X=$(false) || echo $?
1

You could use exit $? above instead.

But otherwise it will be lost and remaing a success.

$ echo $(false)

$ echo $?
0

Get status for subshell

From Superuser.com.

How do I get the output and exit value of a subshell when using bash -e? Using $() preserves the exit status. You just have to use it in a statement that has no status of its own, such as an assignment.

OUTPUT=$(INNER)

Exit on error

Basic

my-cmd || exit $?

# This will only run if `my-cmd` succeeded.
# ...

Or

my-cmd

if [[ $? -ne 0 ]]; then
  echo 'Error running my-cmd`'
  
  exit 1
fi

# This will only run if `my-cmd` succeeded.
# ...

Or simply set an attribute to make any errors cause an exit.

set -e

my-cmd

# This will only run if `my-cmd` succeeded.
# ...

Subshell

OUTPUT=$(INNER) || exit $?
echo $OUTPUT

Or

if ! OUTPUT=$(INNER); then
  exit $?
fi
echo $OUTPUT

In a function:

whicha () {
  RESULT=$(which "$1")

  if [[ $? -ne 0 ]]; then
   echo "$RESULT"
   return 1
  fi
  
  # ...
}