Input/Output Processing#




Output files to stdout


Sort the lines in a file


Remove repeated lines


Search for patterns in a file


Count the lines, words and characters in a file


Output the first lines of a file


Output the last lines of a file


Split a stream like a pipe tee


Cut a line into multiple fields (you must specify both -d for delmeter, -f for field number)

Building a Pipleline#

In this example I use the spell program to find misspelled words in the spellk file. The uniq program removes duplicate lines but there’s a catch, the repeated lines have to be next to each other. That’s why uniq is always paired with sort to guarantee that duplicates are on adjacent lines. Finally I use a tee to see the output and also capture it to a file.

Counting Words#

The wc program gets it’s name from “word count” but it’s more frequently used to count lines.

The wc command can be useful in a pipeline. Here’s how to count all of the files in your home directory. Note how stderr from find is redirected to /dev/null to suppress error output.

Grepping for Love#

The grep program looks for words inside of text files. It prints the lines where words are located. This demonstration shows the common uses of grep.