while - perform a set of commands multiple times

Synopsis

.. synopsis::

while CONDITION; COMMANDS; end

Description

while repeatedly executes CONDITION, and if the exit status is 0, then executes COMMANDS.

The exit status of the while loop is the exit status of the last iteration of the COMMANDS executed, or 0 if none were executed. (This matches other shells and is POSIX-compatible.)

You can use :doc:and <and> or :doc:or <or> for complex conditions. Even more complex control can be achieved with while true containing a :doc:break <break>.

The -h or --help option displays help about using this command.

Example

::

while test -f foo.txt; or test -f bar.txt ; echo file exists; sleep 10; end
# outputs 'file exists' at 10 second intervals,
# as long as the file foo.txt or bar.txt exists.