2.8. Getting User InputAt this point, you're probably wondering how to get a value from the keyboard into a Perl program. Here's the simplest way: use the line-input operator, <STDIN> .[61] Each time you use <STDIN> in a place where a scalar value is expected, Perl reads the next complete text line from standard input (up to the first newline), and uses that string as the value of <STDIN>. Standard input can mean many things, but unless you do something uncommon, it means the keyboard of the user who invoked your program (probably you). If there's nothing waiting to be read (typically the case, unless you type ahead a complete line), the Perl program will stop and wait for you to enter some characters followed by a newline (return).[62]
The string value of <STDIN> typically has a newline character on the end of it.[63] So you could do something like this:
$line = <STDIN>; if ($line eq "\n") { print "That was just a blank line!\n"; } else { print "That line of input was: $line"; } But in practice, you don't often want to keep the newline, so you need the chomp operator. Copyright © 2002 O'Reilly & Associates. All rights reserved. |
|