Pythian Group

[author's note: personally, I use awk a bunch in MySQL DBA work, for tasks like scrubbing data from a production export for use in qa/dev, but usually have to resort to Perl for really complex stuff, but now I know how to do .]

Basics:
By default, fields are separated by any number of spaces. The -F option to awk changes the separator on commandline.
Print the first field, fields are separated by a colon.
awk -F: '{print $1}' /etc/passwd

Print the first and fifth field:
awk -F: '{$print $1,$5}' /etc/passwd

Can pattern match and use files, so you can replace:
grep foo /etc/passwd | awk -F: '{print $1,$5}'
with:
awk -F: '/foo/ {print $1,$5}' /etc/passwd

NF = built in variable (no $) used to mean “field number”
This will print the first and last fields of lines where the first field matches “foo”
awk -F: '$1 ~/foo/ {print $1,$NF}' /etc/passwd

NF = number of fields, ie, “7″
$NF = value of last field, ie “/bin/bash”
(similarly, NR is record number)

Read the rest of this entry . . .

Recently I had an interesting issue crop up. Due to an unfortunate migration incident in which involved master/master replication and not checking to see if replication was caught up, we ended up with an infinite replication loop of a number of SQL statements. awk helped immensely in the aftermath cleanup.

The basics of the replication infinite loop were Read the rest of this entry . . .