Command Lists

Command lists are a mechanism used to execute multiple independent commands at once, either sequentially or concurrently. Sequentially, they can be used to run each command one after another (simple sequential execution) or run each command depending on the success or failure of the previous one (dependent execution). However, before we understand how command lists work, we need to learn the concept of exit codes.

When any program or command exits, it returns a number, called the exit code, to the shell. This number is zero if the command completes successfully and non-zero otherwise. Exit codes are also sometimes referred to as return values.

Command List Operators

Command lists are formed by stringing together commands with an operator in between, such as the ; operator, & operator, and the && or || operators. Now, let's look at each of these operators in detail.

Semicolon Operator

The ; operator is quite simple and is used to execute...