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UNIX in a Nutshell: System V Edition

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if



if

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 after the else if and continue checking). For more examples, see "Expressions" earlier in this section, or 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


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