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Simple commands, pipelines and sequences

A simple command is a sequence of words, the first of which specifies the command to be executed. A series of simple commands joined by `|' characters forms a pipeline. The output of each command in a pipeline is connected to the input of the next.

Simple commands and pipelines may be joined into sequences with `;', and will be executed sequentially. Commands and pipelines can also be joined into sequences with `||' or `&&', indicating, as in the C language, that the second is to be executed only if the first fails or succeeds respectively.

A simple command, pipeline or sequence may be placed in parentheses, `()', to form a simple command, which may in turn be a component of a pipeline or sequence. A command, pipeline or sequence can be executed without waiting for it to terminate by following it with an `&'.

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