command sed delete one or more lines from a file

syntax

reference

		sed '{[/]<n>|<string>|<regex>[/]}d' <fileName> 
		sed '{[/]<adr1>[,<adr2>][/]d' <fileName>

		/.../=delimiters
		n = line number
		string = string found in in line
		regex = regular expression corresponding to the searched pattern
		addr = address of a line (number or pattern )
		d = delete

examples

1. remove 3rd line

        $ sed '3d' filename.txt
   

2. remove the line containning awk

        $ sed '/awk/d' filename.txt
   

3. remove the last line

        $ sed '$d' filename.txt
   

4. remove all empty lines

        $ sed '/^$/d' filename.txt
        $ sed '/./!d' filename.txt
   

5. remove the line matching by a regular expresstion

        $ sed '/[0-9/][0-9]*$/d' filename.txt
   

6. remove lines between 7 and 9

        $ sed '7,9d' filename.txt
   
        $ sed '/-start/,/-end/d' filename.txt
   

• all above examples are only changed at the display of the file

• permanent change

        $ sed -i '2d' filename.txt
        # delete 2ed line and save to filename.txt
  		
        $ sed -i".bak" '2d' filename.txt
        # backup filename.txt to filename.txt.bak
        # delete 2ed line and save to filename.txt