Workshop
The Workshop summarizes the key terms you learned and poses some questions about the topics presented in this chapter. It also provides you with a preview of what you will learn in the next hour.
Key Terms
file redirection Most UNIX programs expect to read their input from the user (standard input) and write their output to the screen (standard output). By use of file redirection, however, input can come from a previously created file, and output can be saved to a file instead of being displayed on the screen.
filter Filters are a particular type of UNIX program that expects to work either with file redirection or as part of a pipeline. These programs read input from standard input, write output to standard output, and often don't have any starting arguments.
standard error This is the same as standard output, but you can redirect standard error to a different location than standard output.
standard input UNIX programs always default to reading information from the user by reading the keyboard and watching what's typed. With file redirection, input can come from a file, and with pipelines, input can be the result of a previous UNIX command.
standard output When processing information, UNIX programs default to displaying the output on the screen itself, also known as standard output. With file redirection, output can easily be saved to a file; with pipelines, output can be sent to other programs.
Exercises
Preview of the Next Hour
The next hour introduces wildcards and regular expressions, and tools to use those powerful concepts. You learn how these commands can help you extract data from even the most unwieldy files.
You learn one of the secret UNIX commands for those really in the know: the secret-society, pattern-matching program grep. Better yet, you learn how it got its weird and confusing name!