Category: Scripting

A loop statement can use any other type of command within the loop, including other loop commands. This is called a nested loop. Care should be taken when using nested loops, because you’re performing an iteration within an iteration, which multiplies the number of times commands...

Although providing command line options and parameters is a great way to get data from your script users, sometimes your script needs to be more interactive. Sometimes you need to ask a question while the script is running and wait for a response from the person...

Sometimes, you may not want to display any output from your script. This often occurs if you’re running a script as a background process. If any error messages occur from the script while it’s running in the background, the shell e-mails them to the owner of the...

You can use the same technique used to redirect STDOUT and STDERR in your scripts to redirect STDIN from the keyboard. The execcommand allows you to redirect STDIN from a file on the Linux system: exec 0< testfile This command informs the shell that it should...

You can use the STDOUT and STDERR file descriptors in your scripts to produce output in multiple locations simply by redirecting the appropriate file descriptors. There are two methods for redirecting output in the script: Temporarily redirecting each line Permanently redirecting all commands in the script...

So far, you’ve seen two methods for displaying the output from your scripts: Displaying output on the monitor screen Redirecting output to a file Both methods produced an all-or-nothing approach to data output. There are times, however, when it would be nice to display some data...

Options are single letters preceded by a dash that alter the behavior of a command. This section shows three methods for working with options in your shell scripts.

Another tool you have in your bash shell tool belt is the shift command. The bash shell provides the shift command to help you manipulate command line parameters. The shift command literally shifts the command line parameters in their relative positions. When you use the shift...