csh/C shell scripts: if statement syntax

Contributor Icon Contributed by Rex Date Icon January 9, 2004  
Tag Icon Tagged: csh shell scripting

Conditional expressions give programs life. The ability to branch makes shell scripts powerful. This recipe shows the basic if then else structure for csh, the C shell.


Basic if statement syntax:

if (condition) then
commands
endif

The addition of one or more else keywords offers additional flexibility:

if (condition) then
commands
else if (other condition) then
commands
else
commands
endif

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  • Dan
    test for the existence of a variable using
    if ($?LD_LIBRARY_PATH == 0) then
    setenv LD_LIBRARY_PATH /usr/lib;
    endif
  • Dan
    A variation of the above would be:

    if ( ! ${?LD_LIBRARY_PATH} ) then
    setenv LD_LIBRARY_PATH /usr/lib
    endif

    Use the {} around variables as a habit since the variable names can often interfere with shell syntax.

    The semicolon at the end is ignored.
  • Dan
    Without concrete examples of how the syntax is actually used, this is almost useless information.
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