\section if if - Conditionally execute a command

\subsection if-synopsis Synopsis
<tt>if CONDITION; COMMANDS_TRUE...; [else; COMMANDS_FALSE...;] end</tt>

\subsection if-description Description
<tt>if</tt> will execute the command CONDITION.  If the condition's exit
status is 0, the commands COMMANDS_TRUE will execute.  If it is not 0 and
<tt>else</tt> is given, COMMANDS_FALSE will be executed.  Hint: use
<a href="#begin"><tt>begin; ...; end</tt></a> for complex conditions.

\subsection if-example Example

<pre>
if test -f foo.txt
	echo foo.txt exists
else
	echo foo.txt does not exist
end
</pre>
will print <tt>foo.txt exists</tt> if the file foo.txt
exists and is a regular file, otherwise it will print 
<tt>foo.txt does not exist</tt>.