Linux — Understanding the Power of SED

sed (short for “stream editor”) is a Unix utility designed to parse and transform text using a simple, compact programming language. It was developed between 1973 and 1974 by Lee E. McMahon at Bell Labs and is now available for most operating systems.

The sed command in Linux is very powerful for parsing and transforming text in a data stream (a file or input from a pipeline). It is commonly used for text manipulation tasks such as searching, finding and replacing, insertion, and deletion.

Using sed for Substitution

Assuming we have the following text file:

$ cat pets.txt
This is my cat
  my cat's name is betty
This is my dog
  my dog's name is frank
This is my fish
  my fish's name is george
This is my goat
  my goat's name is adam

Replace the string “my” with “Tony’s”. The following command should be easy to understand (s represents the substitution command, /my/ represents matching "my", /Tony's/ represents replacing the match with "Tony’s", and /g indicates replacing all matches in a line):

$ sed 's/my/Tony’s/g' pets.txt
This is Tony’s cat
  Tony’s cat's name is betty
This is Tony’s dog
  Tony’s dog's name is frank
This is Tony’s fish
  Tony’s fish's name is george
This is Tony’s goat
  Tony’s goat's name is adam