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.. index:: hush shell
.. _hush:
Hush shell
==========
barebox has an integrated shell: hush. This is a simple shell which
is enough for writing simple shell scripts. Usage of the shell for
scripts should not be overstrained. Often a command written in C is
more flexible and also more robust than a complicated shell script.
Hush features
-------------
variables:
.. code-block:: sh
a="Hello user"
echo $a
Hello user
conditional execution ``if`` / ``elif`` / ``else`` / ``fi``:
.. code-block:: sh
if [ ${foo} = ${bar} ]; then
echo "foo equals bar"
else
echo "foo and bar differ"
fi
``for`` loops:
.. code-block:: sh
for i in a b c; do
echo $i
done
``while`` loops:
.. code-block:: sh
while true; do
echo "endless loop"
done
wildcard globbing:
.. code-block:: sh
ls d*
echo ???
There is no support in hush for input/output redirection or pipes.
Some commands work around this limitation with additional arguments. for
example the :ref:`command_echo` command has the ``-a FILE`` option for appending
a file and the ``-o FILE`` option for overwriting a file. The readline
command requires a variable name as argument in which the line will be
stored.
**NOTE:** hush feels like a normal Unix shell, but it cannot calculate by
itself, i.e. $(($A/2)) won't work. Calculation can however be done
with :ref:`command_let`:
.. code-block:: sh
A=10
let B=$A/2
echo $B
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