Regular Expressions

View a log file without comments or blank lines, assuming comments begin with a # as the first character:

The big space between the square brackets is a single space followed by the characters Ctl-i -> Ctl-v to indicate a tab.

egrep -v '^#.*$|^[         ]*$' /etc/snmp/snmpd.conf

vim regexes

I used the following within vim to modify a hosts file to include FQDN when there were only the short names and IPs:

22,31s/\(192.168.0.\d\{3}\)\s\+\(\a\+\d\=\)/\1	\2.example.com	\2/g

This could be optimized a bit, but I'm new to vim regexes.