Question

I am doing a find and replace with sed, replacing the BASH variable $a (when at the start of a new line) with the BASH variable $b:

sed -i "s#^$a#$b#" ./file.txt

This replaces all matches for ^$a. How can I replace only the first occurrence of ^a within the entire file?

Answer 1

This should work:

sed -i "0,/^\$a/s//\$b/" ./file.txt

You can read more about this at http://www.grymoire.com/Unix/Sed.html#toc-uh-29