bulk search and replace with the silver searcher, awk, sed and xargs

search_and_replace.sh

ag "sometext" --nogroup | awk '{print substr($1,1,index($1,":")-1);}' | xargs -I {} sed -i .bak -e 's/sometext/anothertext/g' {}

Is it possible to make it into a script with arguments?
The default argument names are conflicting with the awk commands...

Yes. The string passed to sed is single quoted so it shouldn't be an issue. The script will just be a little harder to read.

ag "$1" --nogroup | awk '{print substr($1,1,index($1,":")-1);}' | xargs -I {} sed -i '.back' -e "s/$1/$2/g" {}

Here's a small improvement:
ag $1 --files-with-matches | xargs -I {} sed -i '.back' -e "s/$1/$2/g" {}