Linux Pocket Guide, 2nd Edition

File Text Manipulation

grep	Find lines in a file that match a regular expression.
cut	Extract columns from a file.
paste	Append columns.
tr	Translate characters into other characters.
sort	Sort lines of text by various criteria.
uniq	Locate identical lines in a file.
tee	Copy a file and print it on standard output, simultaneously.

Perhaps Linux’s greatest strength is text manipulation: massaging a text file (or standard input) into a desired form by applying transformations, often in a pipeline. Any program that reads standard input and writes standard output falls into this category, but here we’ll present some of the most important tools.