.. _sequence:

Sequences of Commands
======================

.. index:: sequence, ; , ()

Normally, we put one command on each line of input to the shell.  If we want to
run several commands right after another, use ``;`` to separate them.  Using a
pair of parentheses, the output from several commands can also be grouped
together to be redirected as one set of output.  Effectively the same result
could be accomplished by putting the commands in a shell script file.

.. seealso::

    Section 5.9 and 5.10 in the book have some nice examples of this.

Execute three commands in sequence::

    $ date; pwd; ls 

Group the commands to one one output stream::

    $ (date; pwd; ls) > out.txt 

Conditional Execution
----------------------

The following two examples use the :ref:`exit` of the first command to
conditionally execute the second command. A logical **AND** operator, `&&`,
executes the second command only if the first command completed
successfully.

::

    $ gcc myprog.c && a.out

A logical **OR** operator, `||`, executes the second command only if the
first command failed.

::

    $ gcc myprog.c || echo compilation failed