Automating frequent tasks

• create a shell script

• send messages to a terminal

• receive input from a file or terminal

• solve problems

At this point an extended sample shell script is supplied: see ``Writing a readability analysis program: an example''. This example explains how to do the following:

• structure a program

• use the for loop

• get options from the command line

• use the while loop

• use the until loop

• make choices and test input

• use the if statement

• test files, strings and integers

• test exit values

• use logical operators

• use the case statement

• use the select statement

• tune script performance

• control program performance

The syntax described in this chapter is common to the Bourne shell and the Korn shell; for C shell syntax, refer to csh(C) in the Operating System User's Reference.