Here are a bunch of regex exercises. Enjoy!

Match a string consisting entirely of digits.

\d+

Match a string with only alphanumeric characters and with length at least 4.

\p{Alnum}{4,}

Match a string containing two words that are the same. 

.*\b(\w+)\b.*\1.*

Match a string containing 4 consecutive lowercase consonants.

[a-z&&[^euioa]]{4}

Match a person's name, for example Harry Potter. The name is assumed to
consist of two words, each starting with a capital letter and consisting
entirely of letters (from the usual alphabet, without accents). There may be
one or more white space characters separating the two parts.

[A-Z][a-z]+\s+[A-Z][a-z]+

Match a valid postal code, for example M5R 1E4 (with one space in between).

[A-Z]\d[A-Z] \d[A-Z]\d

Match a valid postal code with all digits the same, for example M5R 5E5.

[A-Z](\d)[A-Z] \1[A-Z]\1

Match a string that represents time in HH:mm:ss format. HH is hours between
01 and 12. mm and ss represent minutes and seconds, and each is between 00
and 59. Valid examples include 01:26:18 and 11:00:39. Invalid examples
include 13:01:01, 00:00:00, and 01:00:60.

Consider this file format:

ANA300Y1<T>Y <T>Human Anat Histol <T>LEC<T>0101<T>0350<T>0325<T>000 ANA301H1<T>S
<T>Human Embryology <T>LEC<T>0101<T>0500<T>0500<T>054 ANA498Y1<T>Y <T>Research Project
<T>LEC<T>0101<T>9999<T>0012<T>000 ANT100Y1<T>Y <T>Intro Anthropology
<T>LEC<T>5101<T>1250<T>1129<T>000 ANT200Y1<T>Y <T>Intro Archaeology
<T>LEC<T>5101<T>0300<T>0281<T>000 CSC148H1<T>S <T>Intro to Comp Sci
<T>LEC<T>0102<T>0100<T>0061<T>000 CSC148H1<T>S <T>Intro to Comp Sci
<T>LEC<T>5101<T>0120<T>0117<T>000 CSC148H1<T>S <T>Intro to Comp Sci
<T>TUT<T>0101<T>0060<T>0060<T>000 CSC148H1<T>S <T>Intro to Comp Sci
<T>TUT<T>0201<T>0048<T>0019<T>000 CSC207H1<T>F <T>Software Design
<T>LEC<T>0101<T>0120<T>0096<T>000 CSC207H1<T>F <T>Software Design
<T>LEC<T>5101<T>0085<T>0043<T>000

Lecture Term Course title LEC/TUT? SEC CAP ENRLMT WAITING LIST

You can assume that the number of characters before the first tab character
and between successive tab characters is always the same in every line of
the file.

1) Write a regular expression to match the lecture (“LEC”) sections of
fall-term courses with names beginning “Intro”. Group the course codes
(“XXX123..”) and section numbers (for example, 5203) so that they can be
extracted from the matched substring.

2) The third-to-last and second-to-last columns indicate the enrolment cap
and the actual enrolment. Write a regular expression to match every line
where the enrolment is at the cap.

3) Write a regular expression to match any line where the course title is
shorter than 10 characters, not including trailing blanks. For example, the
course title for CSC148H1 is “Intro to Comp Sci”. There is no need to group
any part of the string, though you may do so if you find it helps. (There
are 30 characters in the course title area of each line. At least the first
character of the title must be non-blank.)