Insert a line at specific line number with sed or awk

Question

I have a script file which I need to modify with another script to insert a text at the 8th line.

String to insert: Project_Name=sowstest, into a file c

Answer 1

An ed answer

ed file << END
8i
Project_Name=sowstest
.
w
q
END

. on its own line ends input mode; w writes; q quits. GNU ed has a wq command to save and quit, but old ed's don't.

Further reading: https://gnu.org/software/ed/manual/ed_manual.html