Linux in a Nutshell, Third Edition

Name

if

Synopsis

if

Description

Begin a conditional statement. The simple format is:

if (expr) cmd

There are three other possible formats, shown side-by-side:

if (expr) then   if (expr) then   if (expr) then
   cmds             
                  cmds1             
                  cmds1
endif            else             else if (expr) then
                    cmds2             
                  cmds2
                 endif            else
                                      cmds3
                                  endif

In the simplest form, execute cmd if expr is true; otherwise do nothing (redirection still occurs; this is a bug). In the other forms, execute one or more commands. If expr is true, continue with the commands after then; if expr is false, branch to the commands after else (or branch to after the else if and continue checking). For more examples, see Section 8.5 earlier in this chapter, shift, or while.

Example

Take a default action if no command-line arguments are given:

                     if ($#argv == 0) then
   echo "No filename given. Sending to Report."
   set outfile = Report
else
   set outfile = $argv[1]
endif