CareerCup

We had this exact problem in my Unix Tools and Scripting Class at Cornell.

grep -Eo "(\(?[[:digit:]]{3}\)?\s*[.-]?\s*)?[[:digit:]]{3,4}\s*[.-]?[[:digit:]]{4}" phone-data.txt | wc -l

#easy way
more filename | grep "[1-9][1-9][1-9][1-9][1-9][1-9][1-9][1-9][1-9][1-9] \| [1-9][1-9][1-9]-[1-9][1-9][1-9]-[1-9][1-9][1-9][1-9]"
#this will preserve 2 formats like
#123456790
# 123-456-7890

grep -o '(*[[:digit:]]\{3\})*-*[[:digit:]]\{3\}-*[[:digit:]]\{4\}'
This will take care of following formats:
1. 1234567890
2. 123-456-7890
3. (123)-456-7890
Also it will take into account multiple phone numbers on same line

grep -c [0-9]\{3\}-[0-9]\{3\}-[0-9]\{4\} < filename>