Here's a cool way to remove "all but the first tag" of a line, in vi:
:s/\([^^]\)<[^<]*>/\1/g

Here's a cool way to split the header from the body of an e-mail,
and save them in seperate files:
sed -e '1,/^$/w 'foo -e '/^$/,$w 'bar

Moving on to actual sed programming, join each line with the next line,
modify that to look like CSV, then delete the next lines:
sed -e '/2007/{h; N; s/\n/,/g; s/ Total files:[[:space:]]//}' -e '/Total/d'

Set time accurately to utcnist.colorado.edu on a windows machine:
net time /setsntp:128.138.140.44

Perl to un-URL-encode test: perl -ne 's/%([A-Fa-f0-9]{2})/pack("c",hex($1))/ge
Modern days: use URI::Escape; $bar=uri_unescape($foo);

20:16 < Norby> mysql> select id, color, style, `style group`, (IFNULL(`style
               group`,style)) as Style2 from `inventory` WHERE 1 LIMIT 0,2;
20:16 < Norby> +------+-----------+----------+-------------+----------+
20:16 < Norby> | id   | color     | style    | style group | Style2   |
20:16 < Norby> +------+-----------+----------+-------------+----------+
20:16 < Norby> | 1000 | Blue      | Plaid    | Woven       | Woven    |
20:16 < Norby> | 1001 | Sassafras | Cascadia | NULL        | Cascadia |
20:16 < Norby> +------+-----------+----------+-------------+----------+

Emacs show CVS diff of current buffer: C-x v =
Emacs show CVS diff of directory: M-x cvs-examin /path/to/work/dir

From Jim Dennis, illustrating good use of sh builtins:
ps wax | while read pid x x x cmd args; do [ $cmd = foo ] && kill $pid; done 

Using perl to split on non-whitespace lists:
echo -n "a,b,c" | perl -anF, -e '{foreach $i (@F) {print "$i\n" ; }}'

How to get grep to NOT show up when grepping ps output:
ps auxww | grep "[f]oo"
or better yet: ps auxww | awk '/pattern/ && !/awk/ {print}'

Continuously kill any process with a port in a port range, till none left:
lsof -t +r -b -P -i :8200-8299 | awk '/^[0-9]/ {system("echo kill " $1)}'

Remove yesterday's file, above a specific size, with no errors:
sudo forallnode k1-k9 "find /e/c/k/hadoop/run2/log -mtime 1 -size +1024000k -print0 | xargs -0r rm"

Python's "for x in ar" is "if grep {$_ eq "foo"} @array;" in perl

getrusage(2) is a system call for a process to find out about its
own resource utilization.


Perl in-place editing:
perl -ni.2004-02-03 -e \"if (!/^dkim:/ && !/^bayard:/ && !/^tarnold:/) {print;}\" /etc/passwd ; if [ -x /usr/sbin/pwconv ] ; then /usr/sbin/pwconv ; fi"

Quick perl truncation (I don't know of a way to do this with sed?):
perl -pe 'chomp; $_=substr($_,0,25)."\n"'
python:
python -c 'import sys; print sys.stdin.readline().rstrip("\r\n ")[:25], "\n"'

Use awk to make pairs of every 40th host:
list-hosts | awk '0 == NR%40 {print}' | awk '{getline n; print "ssh -n", $1, "ping -c 25 -n -q", n, ">! "$1"-"n".ping &"}'