Working with sed and awk
sed, from Stream EDitor, is a command that is used to perform transformations on text. It works from the command line and processes text via standard in and standard out. It does not modify the original input and does not save the output unless you redirect that output to a file. It is most useful this way or when piped between other commands.
awk is a small programming language for processing strings. It takes in text, transforms it in whatever way you tell it to, and then outputs the transformed text. It doesn’t do as much as other languages, but what it does do it does with elegance and speed.
awk run from the command line. There is a lot to them, more than can be covered in a short section of one chapter ...