Datasheet

Phase 1

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Working on the Command Line

This example relies on subtle order effects: On the command line, standard error is redirected

to standard output before standard output is redirected to /dev/null; however, bash interprets

these redirections in the opposite order. Thus, this command will send nothing as input to

text2gif if you reverse the order of the two redirection operators. Also, when redirecting to &1

or &2, you should include no space between the redirection operator and its destination.

Criteria for Completion

This task demonstrated the use of pipe and redirection operators for standard input, standard

output, and standard error. You should now be able to apply these operators in working with

Linux commands that generate textual output or expect textual input. (A few commands, such

as text2gif, generate binary output on standard output and rely on you to be able to redirect

or pipe it appropriately.)

Task 1.8: Manage the Shell Environment

Linux shells are simply programs, and like many programs, the details of their operation can

be customized. You can change the command prompt, set the directories in which the shell

searches for program files, and so on. These features are adjusted via environment variables,

which you can set on the command line or in configuration files. Other programs can also use

environment variables, so in some cases, setting an environment variable in a bash configu-

ration file can affect programs launched from bash.

Scenario

You dislike your current bash prompt and want to change it to something that includes the

date and time. You also need to set an environment variable that tells various programs what

editor to use when calling an external text editor. You want to test these changes and then

make them permanent by modifying your bash configuration file.

Scope of Task

To perform this task, you’ll need to type a few commands at the command line and edit a con-

figuration file. Consult Task 1.5 for information on using Vi for file editing, or use your favor-

ite text-based or GUI editor.

Duration

This task will take about half an hour to complete. Once you know how to change environ-

ment variables, you’ll be able to do so in under a minute—but it may take longer than that to

determine what environment variable needs changing!

83484.book Page 38 Monday, September 18, 2006 8:58 AM