Find lines in multiple files starting with text, and replacing with lowercase

Question

I'm trying to find all files that contains lines that start with a specific string, and then set everything in that line after that to lowercase. I'm able to do parts of what I want but can't seem to figure out how to get it all to work.

Here's an example of the string I'm looking for:

      _assetBundleName: SomeDirectory/ChildDirectory

and I need it to be:

      _assetBundleName: somedirectory/childdirectory

So I can't convert the entire line to lower case, just everything after the string I'm looking for (which is _assetBundleName: ). And I need to perform this on many files (all directories and subdirectories from where the command is run).

sed 's/[a-z]/\L&/g' converts everything to lowercase, not just everything after the string I've found.

Answer 1

You can use this gnu-sed with 2 capture groups:

sed -E 's/(_assetBundleName:)(.*)/\1\L\2/' file

\L\2 will lowercase only the 2nd capture group content.

---

As noted above that this requires gnu-sed. If you don't have that then you can use this awk command:

awk 'BEGIN {FS=OFS=":"} 
$1 ~ /_assetBundleName/ {$2 = tolower($2)} 1' file