Perl Sample Code

• example.pl
  This isn't a program so much as snippets of Perl code. The comments try to tell you what the snippets do. Looking at the code and what it outputs together will also help tell you what it does.

  You can try out these snippets (or any Perl snippets) like this:

  • perl -d -e 0 gets you into interactive perl
  • Now type lines of code. (Do not use "my" to declare variables. They'll be created in a context that disappears as soon as the line is executed, and so are counterproductive when using the interactive debugger).
  • A new line ends a statement - not just a semicolon.

  Example invocation: ./example.pl
  Another way: perl example.pl

  (The first way works only if the file has execute permission.)

• plwc.pl
  An implementation of the word count assignment, in perl.

  Example invocation: ./plwc.pl myInputFile

• plgrep.pl
  Implements a very primitive version of the Unix program grep.

  General invocation:./plgrep.pl 'perl_regular_expression' inputfile
  Be careful with the regular expression. Quote it with apostrophes.

  Example invocation:./plgrep.pl '\s\w*a\w*e\w*i\w*o\w*u\w*\s' inputfile
  Looks for a word (preceded and followed by white space) in which the vowels appear in order.
  Note: This program gives you what is in some cases a handy way to test/debug perl regular expressions you want to use in some program.

• plawk.pl
  A program in the spirit of the awk program. All it does is read its input and break it up into tokens (which is a key feature of awk).

  Example invocation:./plawk.pl inputFile

• userShell.pl
  Processes the /etc/passwd file to print the login shell and username of each user.

  Example invocation: ./userShell.pl