Simple bash refactoring function (depends on SilverSearcher)

refactor.sh

# Usage:
# First, search files recursively for text using ag (SilverSearcher). This could be refactored to use grep probably
# $ refactor gen 'function' > lines.txt
# Lines.txt will contain the file paths, line numbers, and line contents like so: (one entry per line)
# index.js:52:            handler: function onNext() {
# Now, using your favorite editor, edit the lines.txt file with any changes you want to make to those lines (using something search replace, a text editor, or a bash script)
# Save the file and now run the script again to update all the files accordingly:
# refactor run lines.txt

# Note: You can also use `refactor dry lines.txt` to show the changes that will be made
# Note2: Make sure that you run the script from the same directory and that you don't make line-numbering changes between gen and run

function refactor {
    case $1 in
        # This will search using ag (SilverSearcher) for lines that contain the regex provided
        gen)
            PATTERN=$2
            ag --noheading $PATTERN | awk NF
        ;;

        dry)
            CHANGE_FILE=$2
            cat $CHANGE_FILE | while read line
            do
                # The relative file path
                F=${line%%:*}
                
                # The line number
                LINE=${line#*:}
                LINE=${LINE%%:*}
                
                # The replacement line from the lines file
                REPL=${line#*:}
                REPL=${line#*:}
                
                # Pull the existing line from the file
                EXISTING=`cat $F | head -n $LINE | tail -n 1`
                
                echo $F:$LINE
                echo -e '\t\e[31m'$EXISTING
                echo -e '\t\e[32m'$REPL
                echo -e '\e[39m'
            done;
        ;;

        run)
            CHANGE_FILE=$2
            cat $CHANGE_FILE | while read line
            do
                # The relative file path
                F=${line%%:*}
                
                # The line number
                LINE=${line#*:}
                LINE=${LINE%%:*}
                
                # The replacement line
                REPL=${line#*:}
                REPL=${REPL#*:}
                
                # Hack the text before and after the line off and splice in the changed line. Output to a tempfile
                { cat $F | head -n $((LINE-1)); echo $REPL; cat $F | tail -n +$((LINE+1)); } > /tmp/refactortmp.txt
                
                cat /tmp/refactortmp.txt > $F
                rm /tmp/refactortmp.txt
            done;
        ;;

        *)
            echo "Usage:"
            echo
            echo "First, search files recursively for text using ag (SilverSearcher). This could"
            echo "be refactored to use grep probably"
            echo "    $ refactor gen 'function' > lines.txt"
            echo
            echo "Lines.txt will contain the file paths, line numbers, and line contents like so:"
            echo "(one entry per line)"
            echo "    index.js:52:            handler: function onNext() {"
            echo
            echo "Now, using your favorite editor, edit the lines.txt file with any changes you"
            echo "want to make to those lines (using something search replace, a text editor, or"
            echo "a bash script)"
            echo
            echo "Save the file and now run the script again to update all the files accordingly:"
            echo "    refactor run lines.txt"
            echo 
            echo "Note: You can also use 'refactor dry lines.txt' to show the changes that"
            echo "will be made"
            echo
            echo "Note2: Make sure that you run the script from the same directory and that"
            echo "you don't make line-numbering changes between gen and run"
        ;;
    esac
}