Sed insert before first match

Question

I want to insert a string in html before the first "<p" in the file, however I am having some difficulty.

thestring="<p>this is some sentence</p>"
sed -i "/<p/i${thestring}" somefile.html

"somefile.html" however contains multiple lines containing "<p" and the above inserts the string multiple times.

I have tried doing this:

sed -i "0,/<p/i${thestring}" somefile.html

or

sed -i "0,/<p/s//i${thestring}" somefile.html

but I'm getting no where.

What am I doing wrong?

this link may help: http://stackoverflow.com/questions/148451/how-to-use-sed-to-replace-only-the-first-occurrence-in-a-file — user1502952, Nov 20 '13 at 11:11

score 2 · Accepted Answer · answered Nov 20 '13 at 11:21

2

two things you may consider :

1) use s/.../.../ instead of i

2) special chars in your thestring which would conflict with sed's s separator. In your example the slash in/p>

this should work for your needs:

 sed  -i "0,/<p/ s_^_$thestring\n&_" file

answered Nov 20 '13 at 11:21

Kent

1

It doesn't work for me - $thestring is substituted in before every line until the desired line, instead of just before the desired line. – Robin Green Jan 21 '16 at 17:51
@RobinGreen specify the exact range of lines `sed 2,4...` rather than `0,... ` – Max Power Sep 21 '22 at 18:07
@MaxPower The problem is you don't necessarily know the line numbers in advance – Robin Green Sep 23 '22 at 05:34

score 0 · Answer 2 · answered Nov 20 '13 at 11:30

0

echo "${thestring}" | sed s'@<p>this is@blah blah <p>this is@'

If you want to get a specific instance of "

", just add a bit more context for the search.

answered Nov 20 '13 at 11:30

petrus4

2 Answers2