Question

For example , A text file has:

dfsdfsd
f
dsf
dsf
dsf
dsf
sdafadfdasfdsfd
sf
sdfasdfdasfdsfsdf
sd
fsdfdsaf

Then , i would like to find a way to obtain the line number of sf
and insert a paragraph before sf

Are there any ways to doing it in bash programming ???thanks

Answer 1

If you want to find out the line number, you could use grep -n.

If you just want to insert a line on the preceding line, you could use sed like this:

sed "s/sd/paragraph\nsd/" file

This will insert the text “paragraph” above the line with “sd”.

To only do this for the first match:

sed "0,/sd/ { s/sd/paragraph\nsd/ }" file

Here, we only match lines until the first matching “sd”, so any later sd’s will not match.