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Linux Awk Simple Example




Awk is a programming language included in Linux flavors of OS'es which is typically used for data extraction.

Or in a layman term Awk is a utility tool to simplify the life of a lazy and a smart System Administrator when digging out information from a large text file.

Often Awk is combined with regexp (regular expression) and also with the side utility tool.

That's why, if you search on the internet your search will see some examples that Awk is combined with Sed for more complex searching but with accurate results.

Before going on to complex stuff, start with the basic or a simple command to get started. When the complex stuff comes in, with the right or solid foundation it will be easier to understand.

But of course, if you find simple stuff is a piece of cake, go ahead and dive in right away to complex stuff.

Here's a basic and simple example of Awk.

The input is piped or taken from the output of DF -h.

df -h | awk '/mnt/ { print $0}'


   Sample output:

                      5.5T  4.5T 1006G  82% /mnt/NAS01

                      5.5T  4.5T 1006G  82% /mnt/Cloud01

So awk will search from the output of df and look or search for "/mnt" and tells Awk to print the output.

So all the mounted devices or "/mnt" string from df will be filtered and shown as output of the Awk command.

The input from above example is piped to Awk.

Here's another example:

 awk '/(PERC 6\/i Integrated)/ { print $0 }' /var/log/messages

  Sample output:



        Feb  2 20:58:00 Machine1x Server_Administrator: 3367 2242 - Storage Service  The Patrol Read has started.:  Controller 0 (PERC 6/i Integrated)

        Feb  3 01:23:03 Machine1x Server_Administrator: 3367 2243 - Storage Service  The Patrol Read has stopped.:  Controller 0 (PERC 6/i Integrated)


The Awk search for the string "(PERC 6\/i Integrated)" from  /var/log/messages and prints the matching string.

Notice in the input that there is "\/" in "(PERC 6\/i Integrated)" string, but the matching output is: (PERC 6/I Integrated)

The backslash character "\" if it is interpreted literally, the function of "\" in the Awk command tells Awk that the following character is part of the input string.

So the literal string that Awk will search for is:  (PERC 6/i Integrated)

If the "escape" character or the backslash key is omitted awk will display an error such as: awk: fatal: Unmatched ( or \(: /(PERC 6/

It will have an error, so for matching characters like "/" has to be preceded by "\" so awk will interpret the character as part of the input string.

If you want to dig further or tired of simple and basic stuff, check out this link for more examples: https://www.gnu.org/software/gawk/manual/html_node/Very-Simple.html

Cheers.. till next time.. hope it helps.. have fun.

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