Sed

replace string

sed -e 's/\/.*\///g'

• remove /.*/ (directory structure from file)

join ldif lines together

sed -e :a -e '$!N;s/\n //;ta' -e 'P;D' file

• Append lines that start with a space to the previous line

insert a line after a specific line number

sed -i "3i hello" t.txt

• Insert a line at the 3rd line of the file t.txt that says “hello”
• -i is to replace the existing file rather than creating new.

sed -i "6i exit 0;" dirinit.sh 

• insert “exit 0;” after the 6th line of the file

delete a specific line

sed -e '/uniquemember: cn=null/Id' test.ldif

• delete lines that match string
• I = case insensitive

convert to lowercase

sed -e 's/\(.*\)/\L\1/'