Bash - run command until success

How to run a command repeatedly until it succeeds:

passwd
while [ $? -ne 0 ]; do !!; done
 

The !! is a shortcut to the last command run. Run the command once and then the while loop will execute until the command succeeds (i.e. returns 0)

If you’re serious about Bash scripting - check one of these books out:

• Learning the bash Shell: Unix Shell Programming (In a Nutshell (O’Reilly))
• Linux Command Line and Shell Scripting Bible, 3rd Edition
• bash Cookbook: Solutions and Examples for bash Users