Delete Lines With Sed

Deleting lines with sed command is quite simple if you understand the trick.

And the trick is that it follows this pattern mostly:

sed 'nd' filename

Think of it as "delete n".

I know that doesn't give much information but it will be more relatable when you see the sed command examples for deleting lines I am going to share in this article.

I'll be using this sample file called lines.txt in the examples. It will be easier to follow with this text content.

Line number 1
Line number 2
Line number 3
Line number 4
Line number 5
Line number 6
Line number 7
Line number 8
Line number 9
Line number 10

Delete the first line

This is simple. Just use 1d like this:

sed '1d' filename

And here's an example of the command in action:

abhishek@LHB:~$ sed '1d' lines.txt 
Line number 2
Line number 3
Line number 4
Line number 5
Line number 6
Line number 7
Line number 8
Line number 9
Line number 10

Delete a specific line number

To delete the nth line of a file, just provide the number in this manner:

sed 'nd' filename

Let's say I delete the 4th line in my example here:

abhishek@LHB:~$ sed '4d' lines.txt 
Line number 1
Line number 2
Line number 3
Line number 5
Line number 6
Line number 7
Line number 8
Line number 9
Line number 10

If the number exceeds the total lines in the file, no line is deleted.

Delete the last line

In the previous examples. you specified the line number. Deleting the first line was easier as you used 1d but you won't always know the last line number. You can get that info for sure but there is a much easier way to remove the last line with sed:

sed '$d' filename

Here, $ represents the last line and d is for delete (and you know that already).

abhishek@LHB:~$ sed '$d' lines.txt 
Line number 1
Line number 2
Line number 3
Line number 4
Line number 5
Line number 6
Line number 7
Line number 8
Line number 9

Delete range of lines

If you want to delete a specific range of lines from the text file, that can be easily done with sed like this.

To remove lines starting from line number x and going till line number y, use sed command like this:

sed 'x,yd' filename

In the example below, the command removes the line from 4 to 6:

abhishek@LHB:~$ sed '4,6d' lines.txt 
Line number 1
Line number 2
Line number 3
Line number 7
Line number 8
Line number 9
Line number 10

Needless to say that smaller number should be used first and bigger later.

Delete selective lines

Not everything can be grouped into range. What if you want to delete a selected few lines? You can use their line numbers in this manner:

sed 'xd,yd,zd' filename

Let's say, I want to delete lines 5,7 and 9:

abhishek@LHB:~$ sed '5d;7d;9d' lines.txt 
Line number 1
Line number 2
Line number 3
Line number 4
Line number 6
Line number 8
Line number 10

Delete all lines except specified lines

Sed command also supports negation and you can use it to remove all lines except the Nth line or the given range of lines.

To delete all lines except 1st, use:

sed '1!d' filename

To delete all lines except last, use:

sed '$!d' filename

To delete all lines except 5th line, use:

sed '5!d' filename

To delete all lines except lines from 4 to 6, use:

sed '4,6!d' filename

Delete all empty lines

To delete all blank lines, use the sed command in this manner:

sed '/^$/d' filename

Keep in mind that if a line only contains single space, it won't be deleted with the above command.

Delete all lines starting or ending with a certain letter

You can bring simple regex in the play and use it to delete lines based on pattern.

For example, to delete all lines start with letter L, use:

sed '/^L/d' filename

Yes, it is case sensitive.

Similarly, you can delete all lines that end with a certain character/word:

sed '/L$/d' filename

Delete all lines containing a word or pattern

Actually, the above few examples could be grouped in this one because all of them are deleting lines that follow a pattern.

sed '/pattern/d' filename

In our example, let's delete lines containing Line number 1:

abhishek@LHB:~$ sed '/Line number 1/d' lines.txt 
Line number 2
Line number 3
Line number 4
Line number 5
Line number 6
Line number 7
Line number 8
Line number 9

The possibilities are endless. Once you understand the pattern, it becomes easy.

If you are new to SED, I recommend this guide to get started with it.

Getting Started With SED Command [Beginner’s Guide]

Learn to use one of the most powerful commands of the Unix toolbox: sed, the stream editor with practical examples of SED commands.

Linux HandbookSylvain Leroux