Linux: Find text in a large number of files

If you need to find a string in a file, you would typically use:
grep -H "string to find" filename.ext
However, grep doesn’t handle a large number of files well. If you specify grep "string" * or even grep "string" `find ./`you may find yourself facing this error:
bash: /bin/grep: Argument list too long
If you need to search for a string in a lot of files then you can use a simple bash script to do the searching for you.

In this sample, I am looking for a string “sample string” in a directory named “./sample/”:
for i in `find ./sample/`; do grep -H "sample string" $i; done
This uses the find command to do the searching. It actually returns a list of filenames, which we can then grep one-by-one. The -H option tells grep to let us know the filename it found the string in so we can go right into that file to find the location of it.