read a key from keyboard without ReadKey module 1

[msc0tt]

I wish to read a key (other than ENTER) from the keyboard. Is there a way to modify the behaviour of <STDIN> so that it returns each keystroke in the stream, without waiting for ENTER?

Note: we can assume this code will always run on a Linux box.

Note 2: I see that there is a Perl module (Term::Readkey) that can do this. My system does not have this module by default, so I presume others also don't. When developinging, I prefer to write my code as dependency-free as possible. This is why I'm trying to 'reinvent' this wheel.

-with thanks
Mike

 

[MikeLacey]

well... leaving aside the (lack of) merits re wheel re-invention

I used to do this in shell scripts -- on the system I was on the command:

stty raw

gave you character by character

I think, anyway.... It's been a while, it was an stty command anyway.

Mike

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[raider2001]

Mike is right, 'stty raw' will do it. Here's an example:

system(&quot;stty raw&quot;
print &quot;Press y or n: &quot;;
$answer = getc(STDIN);
system(&quot;stty cooked&quot;

 

[msc0tt]

Thanks Mike/Raider,

Works very well. This has progressed into another issue. The cursor keys feed what appears to be three codes into STDIN; code 27 (ESC) followed by two other codes. Is there a way to pre-check STDIN to see if there are additional characters to be read?

Also, I ultimately wish to suppress the key's output to the screen when it is pressed. I will research stty for the correct switch, but if anyone knows offhand?????
-thanks again.

 

[raider2001]

You can try just reading until you get what you want like this:

system("stty raw");
print "Press y or n: ";
do {
    $buffer = getc(STDIN);
    $answer = $answer . $buffer;
} until ($answer =~ m/\w/); # Adjust condition to your liking
system("stty cooked");

 

[msc0tt]

Well!!!!!
Dammed if it doesn't work!! I'm not sure what the &quot;condition&quot; does, but who cares! ;-{)

Thanks, Raider!

 

[raider2001]

The line '($answer =~ m/\w/);' is true when the variable $answer contains a word character. Word characters are a-Z and 0-9.