Sed

Find and replace a line:

sed -i 's/foo/bar/g' FILENAME

Search for terms at the beginning of each line with or without whitespace:

sed 's/^foo *= *1/bar=0/'

Append a new line after a search result:

sed  '/RESULT/ a NEWLINE'

String multiple commands together:

sed -e 's/^foo *= *1/#foo=1/; /#foo=1/ a bar=0'

Replace // with / easily:

sed 's_//_/_g'

Delete all lines with --:

cat FILENAME | sed '/--/d'

Replace the first space in a line with an @ symbol:

sed 's/ /@/'

Grab a single line from a log file:

sed -n '<number>{p;q}' <file>

So for line 46 in main.php:

sed -n '46{p;q}' main.php

Copy a range of lines to a new file:

1. Tail the log to get the date format:

tail /usr/local/apache/domlogs/example.com | head -n1

2. Use grep -n to get the line range:

grep -n "29/Jun/2012:14:15"  /usr/local/apache/domlogs/example.com | head -n1
grep -n "29/Jun/2012:15:36"  /usr/local/apache/domlogs/example.com | tail -n1

3. Use sed to copy those lines and everything in between to a new file:

sed -n '19081,26356p' /usr/local/apache/domlogs/example.com >> /root/newfile

Or just find the range of text you need if you don't know the line numbers:

sed -n '/BEGIN CERTIFICATE/,/END CERTIFICATE/p' ssl.txt

Nix characters

Nix the last character of stout: Pipe into:

sed s/.$//

Nix the last 3 characters of a string:

sed "s/...$//"

Keep only the last 3 characters of a string:

sed "s/.*\(...$\)/\1/"

Nix lines from stdout:

Pipe your command into these: Nix the first line:

sed -n '1!p'

Nix the first three lines:

sed -n '1,3!p'

This lets you do an ls for a vertical list of files for a for loop, like so:

ls -l | sed -n '1,3!p' | rev | cut -d' ' -f1 | rev

For cPanel users from userdata dir:

ls -l /var/cpanel/userdata | sed -n '1,3!p' | rev | cut -d' ' -f1 | rev | cut -d '/' -f1 | grep -v nobody

Or you might want to nix the file extension too, to make backups:

for i in $(ls -1 | sed -n '1,2!p' | cut -d '.' -f1); do cp -a $i.png $i-old.png; done