Chaining Unix Commands

Say, you want to execute a command only if another command is successful then you use &&.

And if you want a command to be executed if another command has failed, you use ||.

1. Create a file tea_ready:

   touch tea_ready
   

2. The following command would print "Tea is ready" if tea_ready file exists:

   ls -l tea_ready && echo "Tea is ready"
   

3. Delete the file tea_ready:

   rm tea_ready
   

4. Check the command from #2 again:

   ls -l tea_ready && echo "Tea is ready"
   

5. The following will print "Tea is not ready":

   ls -l tea_ready || echo "Tea is not ready"
   

6. You can use brackets to avoid confusion:

   (ls -l tea_ready && echo "Tea is ready") || echo "Tea is not ready"