Use grep to quickly count occurrences of a string in a file

Here’s a neat one-liner for counting the number of times a string appears in a file.

cat myfile.txt | grep 'foo' -o | wc -l

This will print the number of times the string foo appears in myfile.txt.

Ofcourse, I could just open a modern text editor and use its find word feature but sometimes I just want to feel smart.