Unix: combine commands with control operators

• Run the second command only if the first command return a zero exit status

• cd a/b/c && tar zxvf ~/archive.tar.gz
  

• the command above extracts archive.tar.gz to a/b/c directory if a/b/c exists.
• Run the second command only if the first command return a non-zero exit status

• cd a/b/c || mkdir -p a/b/c

• the command above create a/b/c directory, if it does not exist
• You can also chain the commands with both operators: 

• cd a/b/c || mkdir -p a/b/c && tar zxvf ~/archive.tar.gz

• the command above make directory a/b/c and extracts archive.tar.gz into it.