Insert blank line in UNIX after different number of lines

sed

Suppose I have a file abc.csv with below data:

abc
def
geh
ijk
lmn
opq
rst

Now, I want to insert blank lines after line2 and line 6.

Please suggest which command shall I use.

Best Answer

$ seq 10 | sed '2G;6G'
1
2

3
4
5
6

7
8
9
10

The G sed command appends a newline followed by the content of the hold space (here empty as we don't put anything in it) to the pattern space. So it's a quick way to add an empty line below that matched line.

Other alternatives are the a and s command:

sed '2a\

6a\
'

Or:

sed '2s/$/\
/
6s/$/\
/'

Some sed implementation also support:

sed '2s/$/\n/;6s/$/\n/'

Related Solutions

How to insert lines with numbers from X to Y into another file after line Z

If your system has the GNU version of sed, you can use the GNU extension r command:

r filename
    As a GNU extension, this command accepts two addresses.

    Queue the contents of filename to be read and inserted into the
    output stream at the end of the current cycle, or when the next input 
    line is read. Note that if filename cannot be read, it is treated as 
    if it were an empty file, without any error indication.

    As a GNU sed extension, the special value /dev/stdin is supported for 
    the file name, which reads the contents of the standard input.

For example,

$ sed '3r /dev/stdin' 123.txt < <(sed -n '2,4p' abc.txt)
1
2
3
b
c
d
4
5

How to insert multiple blank lines after every line

That's the job for sed:

sed -e 'G;G;G;G;G' file

With awk:

nawk -vORS='\n\n\n\n\n\n' 1 file

Or shorter version:

awk 'ORS="\n\n\n\n\n\n"' file

or avoid setting ORS for each input line:

awk 'BEGIN{ORS="\n\n\n\n\n\n"};1' file

Best Answer

Related Solutions

How to insert lines with numbers from X to Y into another file after line Z

How to insert multiple blank lines after every line

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