Esteemed Monks,

I just stumbled upon something I have searched for a couple of times without success. It involves how to clear a screen within an interactive Perl program.

It might seem an obvious thing, but believe me, for a novice, who has shaky Unix knowledge in the first place, this is a useful ability: to be able to wipe the screen in simple interactive programs. It might even be educational-- there are all kinds of other system commands they might think to learn and employ.

All that said, this is my draft of a Q & A, with comments welcome, and with suggestions for where it might go even more welcome. Maybe we could make a novice/misc Q & A section? And what about making a table somewhere in the Q & A or Tutorials section, of common systems commands and what they do?

How do I clear the screen?

Sometimes, in a program, you want all previous inputs to disappear, for aesthetic or other reasons. When you want this to happen, add this line to your program at the appropriate spot:

system "clear";

An example follows: part of a program to interactively quiz a child on his times tables. Note text in <> is pseudocode, except for  "<STDIN>":

while (my $exit = 0)
   {
   <generate question variables randomly and calculate solution>
   print "$mult1 * $mult2 = ?\n";
   chomp ($guess = <STDIN>);
   <test whether $guess = $solution; if so>
   print "Good job! Want to play again? (Y/N)\n";
   <test answer here; if Y, then>
   system "clear";
   }
   <program loops back and pick another pair of numbers and caculates 
+their product>
[download]

Note that I was going to post this as a question in SoPW, until I stumbled across another system command, and wondered what would happen if I substituted "clear" where that other command was. But I remember a time when I didn't know "clear" was a Unix command. Hence this little Q & A. Thanks in advance for your comments.

NovMonk

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