Книга: Fedora™ Unleashed, 2008 edition

Piping Data

Piping Data

Many Linux commands can be used in concert in a single, connected command line to transform data from one form to another. Stringing Linux commands together in this fashion is known as using or creating pipes. Pipes are created on the command line with the bar operator (|). For example, a pipe can be used to perform a complex task from a single command line like this:

$ find /d2 -name '*.txt' -print | xargs cat |
tr ' ' 'n' | sort | uniq >output.txt

This example takes the output of the find command to feed the cat command (via xargs) the name of all text files under the /d2 command. The content of all matching files is then fed through the tr command to change each space in the data stream into a carriage return. The stream of words is then sorted, and identical adjacent lines are removed with the uniq command. The output, a raw list of words, is then saved in the file named output.txt.

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