cardnames.c

//Source: http://home.roadrunner.com/~jgglatt/tech/linuxapi.htm
//cardnames.c
//Lists the names of all sound cards in the system.
//
//Compile as:
//gcc -o cardnames cardnames.c -lasound

#include <stdio.h>
#include <string.h>
#include <alsa/asoundlib.h>

int main(int argc, char **argv)
{
	register int  err;		//Used for checking the return status of functions.
	int cardNum;			//The card number is stored here.
	cardNum = -1;			//ALSA starts numbering at 0 so this is intially set to -1.

	for (;;)
	{
		snd_ctl_t *cardHandle;		//This is your sound card. But not yet. Now it is just a variable.

		//Get next sound card's card number.
		//When "cardNum" == -1, then ALSA
		//fetches the first card
		if ((err = snd_card_next(&cardNum)) < 0)
		{
			printf("Can't get the next card number: %s\n", snd_strerror(err));
			break;
		}

		//No more cards? ALSA sets "cardNum" to -1 if so
		if (cardNum < 0) break;

		//Open this card's (cardNum's) control interface.
		//We specify only the card number -- not any device nor sub-device too
		{
			char   str[64];
			sprintf(str, "hw:%i", cardNum);
			if ((err = snd_ctl_open(&cardHandle, str, 0)) < 0)	//Now cardHandle becomes your sound card.
			{
				printf("Can't open card %i: %s\n", cardNum, snd_strerror(err));
				continue;
			}
		}

		{
			snd_ctl_card_info_t *cardInfo;	//Used to hold card information
			//We need to get a snd_ctl_card_info_t. Just alloc it on the stack
			snd_ctl_card_info_alloca(&cardInfo);
			//Tell ALSA to fill in our snd_ctl_card_info_t with info about this card
			if ((err = snd_ctl_card_info(cardHandle, cardInfo)) < 0)
			printf("Can't get info for card %i: %s\n", cardNum, snd_strerror(err));
			else
				printf("Card %i = %s\n", cardNum, snd_ctl_card_info_get_name(cardInfo));
		}
		// Close the card's control interface after we're done with it
		snd_ctl_close(cardHandle);
	}

	//ALSA allocates some mem to load its config file when we call some of the
	//above functions. Now that we're done getting the info, let's tell ALSA
	//to unload the info and free up that mem
	snd_config_update_free_global();
}