Regular Expression

1. Regular Expression Dr. Tran, Van Hoai Faculty of Computer Science and Engineering HCMC Uni. of Technology hoai@cse.hcmut.edu.vn

2. Text pattern • Used for text-processing utilities • Text-pattern = normal characters + metacharacters = regular expression • Metacharaters in regular expressions are different from those in file name expansion

3. Example (1) • grep [A-Z]* script*.sh • means grep a.txt abc script1.sh script2.sh • grep "[a-z]*" script*.sh • means to find the pattern "[a-z]*" in "script*.sh" • Good and safe solutions are "" and ''

4. Metacharacter sets • Depends on usage context • searching • replacing • Also depends on programs • Different engines • Perl • PHP • .NET regular expression library • Java JDK

5. Searching patterns (1)

6. Searching patterns (2)

7. Example (2)

8. Example (3)

9. Example (4)

10. Example (5)

11. Replacing patterns (1)

12. Example (6)

13. Applications <TAG\b[^>]*>\(.*?\)</TAG> [A-Z0-9._%-]+@[A-Z0-9.-]+\.[A-Z]{2,4}

14. text processing utilities is NEXT