Count number of occurrences of a pattern in a file (even on same line)

Question

When searching for number of occurrences of a string in a file, I generally use:

grep pattern file | wc -l

However, this only finds one occurrence per line, because of the way grep works. How can I search for the number of times a string appears in a file, regardless of whether they are on the same or different lines?

Also, what if I'm searching for a regex pattern, not a simple string? How can I count those, or, even better, print each match on a new line?

Answer 1

Hack grep's color function, and count how many color tags it prints out:

echo -e "a\nb  b b\nc\ndef\nb e brb\nr" \
| GREP_COLOR="033" grep --color=always  b \
| perl -e 'undef $/; $_=<>; s/\n//g; s/\x1b\x5b\x30\x33\x33/\n/g; print $_' \
| wc -l

Answer 2

To count all occurrences, use -o. Try this:

echo afoobarfoobar | grep -o foo | wc -l

And man grep of course (: