Section 2.4. Exercises

2.4. Exercises

You can find the answers to these exercises in "Answers for Chapter 2" in the Appendix.

2.4.1. Exercise 1 [15 min]

Write a program that takes a list of filenames on the command line and uses grep to select the ones whose size in bytes is less than 1000. Use map to transform the strings in this list, putting four space characters in front of each and a newline character after. Print the resulting list.

2.4.2. Exercise 2 [25 min]

Write a program that asks the user to enter a pattern (regular expression). Read this as data from the keyboard; don't get it from the command-line arguments. Report a list of files in some hardcoded directory (such as "/etc" or 'C:\\Windows') whose names match the pattern. Repeat this until the user enters an empty string instead of a pattern. The user should not type the forward slashes that are traditionally used to delimit pattern matches in Perl; the input pattern is delimited by the trailing newline. Ensure that a faulty pattern, such as one with unbalanced parentheses, doesn't crash the program.