while - perform a command multiple times
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Synopsis
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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 <a href="#and">``and``</a> or <a href="#or">``or``</a> for complex conditions. Even more complex control can be achieved with ``while true`` containing a <a href="#break">break</a>.

Example
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::

    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.