What does '$?' mean in bash scripts? [duplicate]

Question

Possible Duplicate:
What does “$?” give us exactly in a shell script?

What does $? mean in a bash script? Example below:

#!/bin/bash
# userlist.sh

PASSWORD_FILE=/etc/passwd
n=1           # User number

for name in $(awk 'BEGIN{FS=":"}{print $1}' < "$PASSWORD_FILE" )

do
  echo "USER #$n = $name"
  let "n += 1"
done

exit $?

Answer 1

$?

is the last error (or success) returned:

$?
1: command not found.
echo $?
127

false 
echo $?
1

true 
echo $?
0

The exit in the end:

exit $?

is superfluous, because the bash script will exit with that status anyway. Citing the man page:

Bash's exit status is the exit status of the last command executed in the script.