Awk

# remove untracked files in mercurial
hg status | grep ^? | awk '{print $2}' | xargs rm

# divide test.log into numbered files based on regex
# to include the line w the regex, leave out "next"
awk -v n=1 '/regexGoesHere/{close(n);n++;next} {print > n}' test.log

# using gawk and a string - version number is padded w zeroes w all log files
LC_ALL=C gawk -v RS='seprator' -v ORS= '{print > "file."sprintf("%03d",NR)}' *.log

# further e.g.
LC_ALL=C gawk -v RS='] Setting User Agent = ' -v ORS= '{print > "chunks/out."sprintf("%05d",NR)".log"}' *.log

Linked from:

Linux Commands