start page | rating of books | rating of authors | reviews | copyrights

UNIX Power Tools

UNIX Power ToolsSearch this book
Previous: 47.2 C Shell Programming Considered Harmful Chapter 47
C Shell Programming...NOT
Next: 47.4 C Shell Variable Operators and Expressions
 

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 47.4 of 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)


Previous: 47.2 C Shell Programming Considered Harmful UNIX Power Tools Next: 47.4 C Shell Variable Operators and Expressions
47.2 C Shell Programming Considered Harmful Book Index 47.4 C Shell Variable Operators and Expressions

The UNIX CD Bookshelf Navigation The UNIX CD BookshelfUNIX Power ToolsUNIX in a NutshellLearning the vi Editorsed & awkLearning the Korn ShellLearning the UNIX Operating System