Mastering Linux Shell Scripting - Second Edition

Displaying and filtering content from files

Now, of course we all want to be able to print a little more than just Hello World. The awk command can be used to filter content from files and, if needed, very large files. We should begin by printing the complete file before filtering it. In this way, we will get a feel for the syntax of the command. Later, we will see how we can add this control information into awk files to ease the command line. Using the following command, we will print all the lines from the /etc/passwd file:

$ awk ' { print } ' /etc/passwd  

This is equivalent to using the $0 variable with the print statement:

$ awk ' { print $0 }' /etc/passwd 

AWK provides us with some ready-to-use variables to extract data such as: