Scan for string across multiple files with R - r

Question

I would like to scan multiple files for strings in R and know which file names have that string.
Is there a way to do this with something like grep, cat, readLines in a function maybe?
If I scan the files using:
fileNames <- Sys.glob("*.csv")
then maybe something like:
for (f in fileNames) {
stuff <- read.csv(fileName, sep = ",")
grep("string")
}
names(res) <- substr(filenames, 1, 30)
Or maybe even better, a loop like this:
for( f in filenames ){
cat("string", file=f)
}
for( f in filenames) {
cat(readLines(f), sep="\n")
}
This code doesn't work, I'm just trying to think this through. Im certain there is a better way to do this. It sounds simple but I cant get it right.
I want to scan files for strings and then have the output of the filenames where the string was found. I have not found an example to do this in R.
Suggestions?

Answer 1

note that in your first code example you use f as a loop variable while inside the loop you use fileName instead (also R is case sensitive so fileNames and filenames are different objects).
if it's unlikely that your search string contains the CSV delimiter, you can indeed use readLines(..) together with grep(..). grep(..) then returns a list of line numbers where the string occurs. Try the following code:
fileNames <- Sys.glob("*.csv")
for (fileName in fileNames) {
if (length(grep("string", readLines(fileName))) > 0) { print(fileName)}
}