Editing C shell (section)

=== Control structures ===

The C shell provides control structures for both [[Conditional (programming)|condition-testing]] and [[iteration]].  The condition-testing control structures are the if and switch statements.  The iteration control structures are the while, foreach and repeat statements.

==== if statement ====

There are two forms of the [[if statement]].  The short form is typed on a single line but can specify only a single command if the expression is true.

<syntaxhighlight lang="csh">if ( expression ) command</syntaxhighlight>

The long form uses then, else and endif keywords to allow for blocks of commands to be nested inside the condition.

<syntaxhighlight lang="csh">
if ( expression1 ) then
    commands
else if ( expression2 ) then
    commands
    ...
else
    commands
endif
</syntaxhighlight>

If the else and if keywords appear on the same line, csh chains, rather than nests them; the block is terminated with a single endif.

==== switch statement ====

The switch statement compares a string against a list of patterns, which may contain wildcard characters.  If nothing matches, the default action, if there is one, is taken.

<syntaxhighlight lang="csh">
switch ( string )
    case pattern1:
        commands
        breaksw
    case pattern2:
        commands
        breaksw
        ...
    default:
        commands
        breaksw
endsw
</syntaxhighlight>

==== while statement ====

The [[While loop|while statement]] evaluates an expression.  If it is true, the shell runs the nested commands and then repeats for as long as the expression remains true.

<syntaxhighlight lang="csh">
while ( expression )
    commands
end
</syntaxhighlight>

==== foreach statement ====

The foreach statement takes a list of values, usually a list of filenames produced by wildcarding, and then for each, sets the loop variable to that value and runs the nested commands.

<syntaxhighlight lang="csh">
foreach loop-variable ( list-of-values )
    commands
end
</syntaxhighlight>

==== repeat statement ====

The repeat statement repeats a single command an integral number of times.

<syntaxhighlight lang="csh">repeat integer command</syntaxhighlight>