What Do Douple Pipes Do?

[shanenin]

I see some bash scripts with double pipes, || , what do they do?

[jcl]

Logical OR. A || B is true if either A or B is true. The shell 'short-circuits' the conditional, so B is only evaluated when A is false, making it a useful control structure. For example, if you have some expression that can potentially fail, you can use || to add simple error-handling code like so

do_something || handle_error

The right-hand side will only be executed if the left-hand side fails.

The shell also provides the logical AND operator '&&' and NOT operator '!'. A && B is true iff both A and B are true, and short-circuits so that B is evaluated only if A is true. Useful for sequencing commands. NOT acts as an inverter: ! A is true when A is false and vice versa.

[shanenin]

those could come in handy. Thanks :-)