Bash script to go through multiple files looking for certain lines using regex (differing between files) and replacing it with the correct corresponding text (different for each file), grabbed from a list in an external file

replace.sh

#!/bin/bash

#Bash script to go through multiple files looking for certain lines using regex (differing between files)
#and replacing it with the correct corresponding text (different for each file), grabbed from a list in an external file

#Expects to be placed in the same directory as the files to search through
#Relies on 2 external files; a list of filenames to edit, and the corresponding replacement text for each file (separated by newlines)

#Used to escape any problematic characters in the replacement text
escapeCharacter() #Takes 2 arguments, the character to escape and the text to escape it from
{
	escapedCharacter="\\"$1
	echo ${2//$1/$escapedCharacter}
}

#The filenames of the lists of files and replacement text
replacementListFilename="replacementlist"
fileListFilename="filelist"

#Creates 2 arrays
replacementList=()
fileList=()

#Assigns all lines from bundlelist to the replacementList array
#Also optionally escapes any characters that aren't regex-friendly, such as a colon; this can be removed and the character to escape can be edited
output=$(cat $replacementListFilename) #relies on a bundlelist file containing all 25 bundles, separated by newlines
characterToEscape=":"
count=0
for i in $output
do
	#replacementList[$count]=$i
	replacementList[$count]=$(escapeCharacter $characterToEscape $i)
	((count++))
done

#Assigns all lines from filelist to the fileList array
output=$(cat $fileListFilename) #relies on a filelist file containing all 25 filenames, separated by newlines
count=0
for i in $output
do
	fileList[$count]=$i
	((count++))
done

regexStart="s/" #Opening of the regex statement
regexSearch="render[(]['].*\//render(\'" #The regex for the text to be searched for; replace with your own regex expression
regexEnd="/g" #This is the required ending of the regex, used by sed when replacing text

#For each of the 25 files... (the number can be edited)
for ((i=0; i <= 24; i++))
do
    echo ${fileList[$i]} #...outputs the filename...
    #...and uses sed to replace the text that is searched for, by the the corresponding replacement text for each file
    sed -i -e $regexStart$regexSearch${replacementList[$i]}$regexEnd ${fileList[$i]}
done