There are three ways awk can be invoked. You can either specify awk on the command line like this:
awk [-F field-separator] 'commands' input-file(s)
where ‘commands’ are the actual awk commands. This method is the one that we will use most in this chapter.
In the above example the use of the -F field separator is optional, as awk uses the <space> as a default field separator. So if you are scanning text which has spaces between fields you don’t have to specify this option; however if you’re scanning the passwd file, for example, then those fields are separated by a colon, so you’ll have to state this with the -F option, like this:
awk -F: 'commands' input-file
The second method is to insert all the awk commands in a file then ...