COP 3344-01 Introduction to Unix: Lecture 9

Learning objectives

After this class, you should be able to:

1. Write simple Perl scripts using the following features: (i) make perl act on each line of a file, (ii) match patterns, (iii) output using print, (iv) perform basic operations on string and numeric variables, (v) read input using <STDIN>, (vi) remove a newline from a string using chomp, (vii) substitute patterns, (viii) use scalar data and variables, (ix) use the default argument $_, and (x) write conditional statements using if and else.
2. Explain the difference between strings that are enclosed in single quotes and those enclosed in double quotes.

Reading assignment

1. JEA: section 35.1-35.11.
2. Lecture slides: Lecture 9.

Exercises and review questions

• Questions on current lecture's material
  1. Write a Perl script that will replace all occurrences of either COP 3344 or COP3344 with COP 3345. Run your script on some sample input file, and store the result in a different output file, using I/O redirection. This feature can be useful, for example, in the following situation. The Computer Science department has a description of courses (see http://www.cs.fsu.edu/current/undergrad/courses.php). If the course number for COP 3344 is changed to COP3345, then this change has to be made throughout the document. Your Perl script can help with this.
  2. Write a Perl script that will prompt the user to input a number, and will output the square of that number.
  3. Modify the pprog5 example so that it outputs the record of all those with GPA over 3.5.

• Questions on next lecture's material
  1. Assume that the default variable $_ contains several fields separated by spaces. Use split to store each field in a separate entry of an array variable named fields.