FAQ 5.31 How can I read a single character from a file? From the keyboard?

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This is an excerpt from the latest version perlfaq5.pod, which
comes with the standard Perl distribution. These postings aim to
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5.31: How can I read a single character from a file? From the keyboard?

You can use the builtin "getc()" function for most filehandles, but it
won't (easily) work on a terminal device. For STDIN, either use the
Term::ReadKey module from CPAN or use the sample code in "getc" in
perlfunc.

If your system supports the portable operating system programming
interface (POSIX), you can use the following code, which you'll note
turns off echo processing as well.

#!/usr/bin/perl -w
use strict;
$| = 1;
for (1..4) {
print "gimme: ";
my $got = getone();
print "--> $got\n";
}
exit;

BEGIN {
use POSIX qwtermios_h);

my ($term, $oterm, $echo, $noecho, $fd_stdin);

my $fd_stdin = fileno(STDIN);

$term = POSIX::Termios->new();
$term->getattr($fd_stdin);
$oterm = $term->getlflag();

$echo = ECHO | ECHOK | ICANON;
$noecho = $oterm & ~$echo;

sub cbreak {
$term->setlflag($noecho);
$term->setcc(VTIME, 1);
$term->setattr($fd_stdin, TCSANOW);
}

sub cooked {
$term->setlflag($oterm);
$term->setcc(VTIME, 0);
$term->setattr($fd_stdin, TCSANOW);
}

sub getone {
my $key = '';
cbreak();
sysread(STDIN, $key, 1);
cooked();
return $key;
}

}

END { cooked() }

The Term::ReadKey module from CPAN may be easier to use. Recent versions
include also support for non-portable systems as well.

use Term::ReadKey;
open my $tty, '<', '/dev/tty';
print "Gimme a char: ";
ReadMode "raw";
my $key = ReadKey 0, $tty;
ReadMode "normal";
printf "\nYou said %s, char number %03d\n",
$key, ord $key;



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