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47.3 Conditional Statements with if

.login and .cshrc files" 1070 is the use of conditionals (if statements). This article explains the syntax of if statements. Article 47.4of explains the syntax of the expressions you can test with an if.

The if command is used to 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 example, the following if clause will 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

For more examples, see article 47.4.

- DG from O'Reilly & Associates' UNIX in a Nutshell (SVR4/Solaris)


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