Beep on Linux in C

Question

I want to generate a beep sound with a specific frequency and length (for different sound signals) using the system beeper (and only the speakers if beeper is not available / accessible). I know it is possible to do this by using ioctl, but that requires root access, which I don't want.

I know I could just use the "beep" command, but that would be a dependency, which, if possible, shouldn't be used (no external dependencies at all, just the basic linux libraries and C).

What I currently have is the following code (but this requires superuser privileges to run):

#include <stdlib.h>
#include <fcntl.h>
#include <linux/kd.h>

int main(int argc, char *argv[])
{
 int fd = open("/dev/console", O_RDONLY);
 if (fd == -1 || argc != 3) return -1;
 return ioctl(fd, KDMKTONE, (atoi(argv[2])<<16)+(1193180/atoi(argv[1])));
}

If there is no other way to do this, then I will use beep, but I would really like to avoid dependencies and integrate the beep directly into my script, but I'm sure somebody here will know a solution / workaround.

I don't really want external libraries as the program should be as lightweight as possible.

Solution 1

I think the only way to do this is to either use suid to give my own program root access, or to use beep, which already has suid. I suppose I will just add one more dependency, then, as beep is not too big anyway.

Thank you for all the answers, I'm sure other libraries are great for more complex signals, but I need a very simple one!

I think this question can be marked as solved / closed, then.

If anybody finds a way to create a beep using the console without superuser-privileges, I'm still interested in this solution :)

Thank you all again.

Solution 2

Please look at the standard linux beep source code. http://www.johnath.com/beep/beep.c

It uses KIOCSOUND ioctl to "beep", but you don't need superuser privileges to make it play. I have configured it to be readable and executable by users on the "beep" group.

So my standard user with UID 1000 is in the group with GID 501 (i called it "beep"). Next to this I had to chmod 4750 /usr/bin/beep and now I'm able to play beeps (in the range 20-20000Hz) without asking for superuser privileges.

Solution 3

The most basic beep is still '\a' , if your terminal supports it:

fprintf(stdout, "\aBeep!\n" );

Solution 4

open("/dev/tty", O_RDONLY); instead /dev/console will work with sound OK for terminal consoles without requiring superuser privileges. But virtual consoles in X session will fail with sound then, even for superuser.

View more solutions

Comments

[omnidan]

I want to keep the program as lightweight as possible

[Basile Starynkevitch]

Then just output a bell character \a and leave the sound making to the terminal emulator. Of course, you can't change the pitch and tone of that sound...

[omnidan]

@BasileStarynkevitch Yeah, of course that's possible, too, but I want specific frequencies to differ the signals a bit.

[omnidan]

Yeah, but that's just one frequency.

[wildplasser]

I said it was basic ... Sorry about that.(the reaction might still be usable for people who visit this page afterwards.)

[U. Windl]

There is a beepcommand, like in github.com/NaWer/beep/tree/master/Music