Read a single tag UID using libnfc.

readtag.c

#include <nfc/nfc.h>

int main ()
{
    nfc_device_t *nfcDev;
    nfcDev = nfc_connect(NULL);

    if (nfcDev == NULL) {
        printf("Cannot connect to the RFID reader.\n");
        return 1;
    }

    nfc_initiator_init(nfcDev);

    // This reader can only get one card ID, so there's no point looking for more
    nfc_target_info_t targetInfo[1];
    int numTargets;

    if (nfc_initiator_list_passive_targets(nfcDev, NM_ISO14443A_106, targetInfo, 1, &numTargets)) {

        int uidPos;
        for (uidPos = 0; uidPos < targetInfo[0].nai.szUidLen; uidPos++) {
            printf("%02x", targetInfo[0].nai.abtUid[uidPos]);
        }

        printf("\n");
    }

    nfc_disconnect(nfcDev);
    return 0;
}