From google:


awk's basic mode of operation is to read its input, chop each line into fields separated by some delimiter (white space by default, but you can change it), and then allow you to do pattern matching and other operations based on those fields. The thing I use it for most often is to grab a particular field.

Let's look at a trusty long ls listing:


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% ls -l
-rw-r--r-- 1 jeffy 28 May 9 16:12 Makefile
-rwxr-xr-x 1 jeffy 24576 May 28 11:31 foo
-rw-r--r-- 1 jeffy 57 May 9 16:13 foo.c
-rw-r--r-- 1 jeffy 57 May 28 11:37 foobar
-rw-r--r-- 1 jeffy 71 Jun 2 11:45 fumpty


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Suppose I want to grab just the file sizes for some reason. awk numbers fields starting with 1 (not zero like you'd expect from a bunch of unix geeks), so we count across and see that we want to print out field 4, so just do this:
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% ls -l | awk '{print $4}'
28
24576
57
57
71


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Easy as pie. Notice that the awk program is enclosed in single quotes. This protects the "$4" from the shell so it gets evaluated by awk, not csh (or whatever)
You can print out multiple columns in any order by separating them with commas:


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% ls -l | awk '{print $3, $1, $4, $NF}'
jeffy -rw-r--r-- 28 Makefile
jeffy -rwxr-xr-x 24576 foo
jeffy -rw-r--r-- 57 foo.c
jeffy -rw-r--r-- 57 foobar
jeffy -rw-r--r-- 71 fumpty


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Notice that the separating white space is not preserved, but gets scrunched down to a single space.
Wait a minute, what's with that "$NF" in that last example? NF is an internal awk variable that always represents the Number of Fields in the current line. By sticking a dollar sign in front of it, I get the equivalent of a "$8" when I run the script on the "ls -l" output. But I don't have to know how many fields there are, I can just grab the last one.


-Thanks .--from your question - it made me learn "awk"!!