\section if if - conditionally execute a command

\subsection if-synopsis Synopsis
\fish{synopsis}
if CONDITION; COMMANDS_TRUE...; [else if CONDITION2; COMMANDS_TRUE2...;] [else; COMMANDS_FALSE...;] end
\endfish

\subsection if-description Description

`if` will execute the command `CONDITION`. If the condition's
exit status is 0, the commands `COMMANDS_TRUE` will execute.  If the
exit status is not 0 and `else` is given, `COMMANDS_FALSE` will
be executed.

In order to use the exit status of multiple commands as the condition
of an if block, use <a href="#begin">`begin; ...; end`</a> and
the short circuit commands <a href="commands.html#and">`and`</a>
and <a href="commands.html#or">`or`</a>.

The exit status of the last foreground command to exit can always be
accessed using the <a href="index.html#variables-status">$status</a>
variable.

\subsection if-example Example

\fish
if test -f foo.txt
    echo foo.txt exists
else if test -f bar.txt
    echo bar.txt exists
else
    echo foo.txt and bar.txt do not exist
end
\endfish

will print `foo.txt exists` if the file foo.txt
exists and is a regular file, otherwise it will print
`bar.txt exists` if the file bar.txt exists
and is a regular file, otherwise it will print
`foo.txt and bar.txt do not exist`.