2. Write down the extended regular expression for following questions.

E.g. Social security number in the format of 999-99-9999. Answer: [0-9]{3}-[0-9]{2}-[0-9]{4}

1) Valid URL beginning with http:// and ending with ".edu" (e.g. http://cs.gsu.edu, http://gsu.edu)

2) Non-negative integers. (e.g. 0, +1, 3320)

3) A valid absolute pathname in Unix (e.g. /home/ylong4, /test/try.c)

4) Identifiers which can be between 1 and 10 character long, must starting with a letter or an underscore. The following characters can be letters or underscores or digits. (e.g. number, _name1, isOK).

5) Phone number in any of the following format: 9999999999,999-999- 9999, (999)-999-9999. (Note: all of these formats should be matched by a single regular expression)