Signed-off-by: Holger Schurig <holgerschurig@gmail.com> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
61 lines
1.3 KiB
ReStructuredText
61 lines
1.3 KiB
ReStructuredText
.. 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::
|
|
|
|
a="Hello user"
|
|
echo $a
|
|
Hello user
|
|
|
|
conditional execution ``if`` / ``elif`` / ``else`` / ``fi``::
|
|
|
|
if [ ${foo} = ${bar} ]; then
|
|
echo "foo equals bar"
|
|
else
|
|
echo "foo and bar differ"
|
|
fi
|
|
|
|
``for`` loops::
|
|
|
|
for i in a b c; do
|
|
echo $i
|
|
done
|
|
|
|
``while`` loops::
|
|
|
|
while true; do
|
|
echo "endless loop"
|
|
done
|
|
|
|
wildcard globbing::
|
|
|
|
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`::
|
|
|
|
A=10
|
|
let B=$A/2
|
|
echo $B
|