awk

awk is a pattern scanning and processing language. However it can be used more simply as a command line filter that operates at the field level rather than the line level like grep does.

A typical awk statement:

awk -F: ‘{print $3}’

This is in two sections. The first is

awk -F: which means use a colon as the field separator
if you used -F” “, that would mean use a space as the field separator

The second part is:

‘{print $3}’

This is saying to print the 3rd field as defined by the field seperator by -F

For example, the passwd file gives us entries such as this line:

root:x:0:0:root:/root:/bin/bash

Here the fields are seperated by colons. The first field is the username, root in this case. So if we want a list of all the users in that file we use:

cat /etc/passwd | awk -F: ‘{print $1}’