Deleting lines

Delete line 5-7 in file

$ sed '5,7d' file.txt

Delete every 2nd line starting with line 3

$ sed '3~2d' file.txt

Delete the last line in file

$ sed '$d' file.txt

Delete lines starting with "Hello"

$ sed '/^Hello/d' file.txt

Delete all empty lines

$ sed '/^$/d' file.txt

Delete lines starting with "#"

$ sed '/^#/d' file.txt