How to replace replace 1 line with 2 lines using sed?

mrjayviper · Sep 7, 2017

I have a very simple text file here with the following contents

Code:

    line1
    line2
    line3
    line4

I want to modify the contents via sed(or some other app) so it becomes

Code:

    line1
    line2
    #this line was added by sed
    line3
    line4

So I tried

sed -e "s/line2/line2\\n#this line was added by sed/" my-text-file-here.txt

but the output is

Code:

    line1
    line2\n#this line was added by sed
    line3
    line4

Any ideas on how to do it correctly? I'm using default shell. Thank you

Jov · Sep 7, 2017

sed -e '/line2/a\
#this line was added by sed'

mrjayviper · Sep 7, 2017

getting an error

Jov · Sep 7, 2017

I test it on bash, works fine.

For tcsh, you may use sed script instead of command line.

Kiiski · Sep 8, 2017

With printf and ed you can do

Code:

printf "%s\n" l 3 i "#this line was added by ed" . w | ed my-text-file-here.txt

But added text will be little different of course

Kiiski · Sep 9, 2017

After good night sleep I noticed there is also a way to do this with sed

Code:

sed -i '.bak' 's:line2:line2\\
#this line was added by sed:' my-text-file-here.txt

By the way, good tutorial about sed:
http://www.grymoire.com/Unix/Sed.html

topcat · Sep 9, 2017

Code:

$ sed -e 's/\(line2\)/\1\
> #this line was added by sed/' file_with_lines
line1
line2
#this line was added by sed
line3
line4