$ grep Mount mountains.txt
grep stands for "global regular expression print". It searches files for lines that match a pattern and returns the results. It is also case sensitive. Here,
grep searches for "Mount" in mountains.txt.
$ grep -i Mount mountains.txt
grep -i enables the command to be case insensitive. Here,
grep searches for capital or lowercase strings that match
Mount in mountains.txt.
The above commands are a great way to get started with
grep. If you are familiar with regular expressions, you can use regular expressions to search for patterns in files.