The three commands covered in this chapter, along with regular expressions (pattern matching), are often grouped together. There are even many books available devoted to awk and sed . In these books, grep usually goes along for the ride because awk is derived to some extent from sed and grep . In addition, the use of regular expressions for pattern matching that are used for awk , sed , and grep are similar.
We'll take a look at regular expressions and pattern matching in general, and then cover the three commands in this chapter: