sed, which stands for stream editor, is a powerful text processing tool used in Linux and other Unix-like operating systems. It performs text transformations on an input stream (a file or input from a pipeline). Here are some common uses of sed:

Substitution#

The most common operation is to replace text in a file. For example:

sed 's/original/replacement/' filename

This command will replace the first occurrence of original with replacement in each line of the file.

Global Substitution#

If you want to replace all occurrences in a line, you use the g flag:

sed 's/original/replacement/g' filename

This replaces all occurrences of original with replacement in each line.

In-place Editing#

By default, sed outputs to the standard output. To save changes back to the file, use the -i option:

sed -i 's/original/replacement/g' filename

This modifies the file in-place.