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Accepting Command-Line Options, Switches, and Parametersng utility uses optional parameters. It creates archives and restores directory and file trees, but it can do so in different ways. The GNU version of tar has roughly 80 different options that can be used in various combinations to tailor the ways in which the utility performs. The major benefit of

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Testing Variables and Assigning Defaultses used for configuration purposes, which are initially set to default values. In this chapter we’ll look at various methods of testing variables and setting default values. The differences between many of these syntactical variants are subtle, but each is useful for working with undefined variables

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cronule. Normally these tasks are performed on systems that run 24 hours a day, 7 days a week. Writing cron scripts to perform system maintenance, backups, monitors, or any other job that you would want to run on a schedule is a very common task. There are a few subtleties with cron however, that many u

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Self-Linked Scriptsns all the code necessary to perform a number of tasks, but you may want to determine the specific task to be performed at runtime by calling the script by a specific name. This lets users invoke an individual task by name without having to learn specialized command-line switches for the options the

explicit

Throttling Parallel Processeslarge environment. With relatively small environments, you could simply write a script that loops through a list of systems and performs the desired task serially on each machine. Another method would be to loop through the list of machines and submit your job to the background so the tasks are perf

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Command-Line Editing and Historyty to recall and modify previous commands quickly and efficiently is beneficial. In the old DOS days, a utility called . would keep your history in a buffer. You could go back or forth through the command history one command at a time by using the up and down arrow keys. Individual commands could be

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Scripting from the Command Lineth me; pretty much anything you can do in a shell script, you can also do from the command line. I’ve coded many ad hoc scripts right at the command line. I wouldn’t recommend writing anything significant that way, but for quickies it’s just the ticket.