How to keep C program running

Question

Hey my program is an RFID reader, a user scans his rfid tag, the rfid tag value is checked in the database, if the value corresponds with the rfid tag database value the door opens and 2 queries are inserted. How do i keep it running? I can only scan one tag, then i need to close the program only then the check will be done including the 2 queries. How can everything be done simultaneously(all code thats in my main)? Do i use a while loop? Thanks

//gcc -o RFID $(mysql_config --cflags) RFID.c $(mysql_config --libs) -std=gnu99 -lphidget21
#include <stdio.h>   
#include <phidget21.h>
#include <stdlib.h>
#include <mysql/mysql.h>
#include <string.h>
#include <time.h>

char tagVal1[10];


int CCONV TagHandler(CPhidgetRFIDHandle RFID, void *usrptr, char *TagVal, CPhidgetRFID_Protocol proto) //Tag wordt gelezen en LED gaat aan
{ 
    CPhidgetRFID_setLEDOn(RFID, 1);


    printf("Tag Read: %s\n", TagVal);
    sprintf(tagVal1, "%s", TagVal);
}

int CCONV TagLostHandler(CPhidgetRFIDHandle RFID, void *usrptr, char *TagVal, CPhidgetRFID_Protocol proto) //Tag is verwijderd van RFID lezer
{
    CPhidgetRFID_setLEDOn(RFID, 0);

    printf("Tag Lost: %s\n", TagVal);
    return 0;
}



int rfid_simple()
{
    int result;
    const char *err;

    //Declare an RFID handle
    CPhidgetRFIDHandle rfid = 0;

    //RFID object wordt aangemaakt
    CPhidgetRFID_create(&rfid);

    //Wanneer de tag gelezen wordt, wordt het uitgeprint
    CPhidgetRFID_set_OnTag2_Handler(rfid, TagHandler, NULL);

    //Wanneer de tag  verwijderd wordt, wordt het uitgeprint
    CPhidgetRFID_set_OnTagLost2_Handler(rfid, TagLostHandler, NULL);

    //RFID wordt geopend voor connectie
    CPhidget_open((CPhidgetHandle)rfid, -1);

    //Programma wacht totdat RFID is aangesloten
    printf("Waiting for RFID to be attached....\n");
    if((result = CPhidget_waitForAttachment((CPhidgetHandle)rfid, 10000)))
    {
        CPhidget_getErrorDescription(result, &err);
        printf("Problem waiting for attachment: %s\n", err);
        return 0;
    }


    CPhidgetRFID_setAntennaOn(rfid, 1);

    //read RFID event data
    printf("RFID reader is aangesloten! Druk op enter om het programma af te sluiten\n");

    //keep displaying RFID event data until user input is read
    printf("RFID tag nodig\n");
    getchar();


    //RFID wordt afgesloten zodra er op Enter wordt gedrukt
    printf("Ik ga afsluiten vriend...\n");
    CPhidget_close((CPhidgetHandle)rfid);
    CPhidget_delete((CPhidgetHandle)rfid);
    return 0;
}
void finish_with_error(MYSQL *conn)
{
  fprintf(stderr, "%s\n", mysql_error(conn)); //foutmelding voor mmysql connectie
  mysql_close(conn);
  exit(1);
}
int main(int argc, char* argv[])
{

MYSQL *conn; rfid_simple(); 

    char* jeMoeder;
    jeMoeder = malloc(150);
    char* jeVader = "Open Deur";
    char *employeeID[20];

    //constants met verbindingsinfo
    const char *server = "" ;
    const char *user = "";
    const char *password =  "";
    const char *database = "";

    //verbinding met de database aanmaken
    conn = mysql_init(NULL);
    if (!mysql_real_connect(conn, server, user, password, database, 0, NULL, 0)){
        fprintf(stderr, "%s\n", mysql_error(conn));
        exit(1);
    }


     if (mysql_query(conn, "SELECT (Employee_id) FROM Employee")){finish_with_error(conn);} // gewoon een select query

  MYSQL_RES *result = mysql_store_result(conn);// opgehaalde data  in results storen

  if (result == NULL){finish_with_error(conn);}

    //We get the result set using the mysql_store_result() function. The MYSQL_RES is a structure for holding a result set.
    //geen zin om dit te vertalen naar NL

  int num_fields = mysql_num_fields(result); // We get the number of fields (columns) in the table.
  const char* rfidTags[num_fields]; // string array declararen

    //We fetch the rows and print them to the screen. en slaat het op in string array

  MYSQL_ROW row;

  while ((row = mysql_fetch_row(result)))
  {
      for(int i = 0; i < num_fields; i++)
      {
          printf("%s ", row[i] ? row[i] : "NULL");
                  rfidTags[i] = row[i];//opslaan in rf[idtag arrays
        if(strcmp(rfidTags[i], tagVal1 ) == 0){
        printf("Tags zijn gelijk, open de deur.");



    //datestamp formuleren voor de sql database
    //bufbaf is de tijdelijke bufferstring voor het opbouwen van de timestamp
    time_t timer;
    char bufbaf[50];
    struct tm* tm_info;

    time(&timer);
    tm_info = localtime(&timer);

    //strftime: print de tijd als een string
    strftime(bufbaf, 30, "%Y-%m-%d_%H:%M:%S", tm_info);
    puts(bufbaf);

    const char* insert = "INSERT INTO Notifications (Notification_id, Notification, Timestamp_Notification) VALUES (NULL, '";
    const char* insert2 = "'";
    const char* insert3 = ",'";
    const char* insert4 = argv[1];
    const char* insert5 = "')";

    char* statementOne;
    statementOne = malloc(strlen(insert) + 1 + 300);

    strcpy(statementOne, insert);
    strcat(statementOne, jeVader);
    strcat(statementOne, insert2);
    strcat(statementOne, insert3);
    strcat(statementOne, bufbaf);
    strcat(statementOne, insert5);

    printf("%s", statementOne, "\n");
    {mysql_error(conn);}
    printf("%s", mysql_error(conn));
    if (mysql_query(conn, ((char*) statementOne)) !=0){
        mysql_error(conn);
    }

    int lastid = mysql_insert_id(conn);
    printf("%d\n", lastid);
    sprintf(jeMoeder, "%ld", lastid);

    const char* insert6 = "INSERT INTO Access(Employee_id, Notification_id) VALUES('";
    const char* insert7 = "',";
    const char* insert8 = ")";

    //nieuwe char array aanmaken voor de uiteindelijke insert command
    char* statementTwo;
    //memory allocaten voor de totale string... ja c is raar en ouderwets
    statementTwo = malloc(strlen(insert6) + 1 + 150);
    //strcpy: string copy, strcat: string concatenate
    strcpy(statementTwo, insert6);
    strcat(statementTwo, tagVal1);
    strcat(statementTwo, insert7);
    strcat(statementTwo, jeMoeder);
    strcat(statementTwo, insert8);

    printf("%s", statementTwo, "\n"); //debugfunctie, print de geformuleerde statement naar de commandline
    //de query: conn is de verbinding met server, statement is de geprepareerde char array met de insert statement
    if (mysql_query(conn, ((char*) statementTwo)) !=0){
        mysql_error(conn);
    }
    mysql_close(conn);

    //printf("%s\n",tagVal1);
    return 0;
        }else{
        printf("Tags zijn onjuist, geen toegang tot de deur");
        }
      }
          printf("\n");

    //for(int a = 0; a < num_fields; a++){
     //printf("%s", rfidTags[a],"\n");}// testen van array: rfidtags
  }
  mysql_free_result(result);


return 0;
}

Answer 1

Although haphazard, you could just throw the whole thing into a "while" loop that goes forever and then just trap the KILL signal. There's some examples kill signal example That will get you started.

A better format for your code would to be an initialization, a run procedure and then a cleanup.