Return from signal handlers

Question

I do not leave the function of the signal handler correctly? It does not seem to return to the program normally. Instead, it goes into a loop and where it should wait for user input, it skips and reads the length of "user input" to -1 and errors. (There will be more meaning in the code.)

void handle_SIGINT() {

    int k = recent;
    int count = 0;
    int stop;

    if (stringSize >= 10) {
        stop = 10;
    }
    else {
        stop = p;
    }

    printf("\nCommand History:\n");

    for (count = 0; count < stop; count++) {

        if (k < 0) {
            k += 10;
        }
        printf("%s", string[abs(k)]);
        k -= 1;

    }

}



void setup(char inputBuffer[], char *args[],int *background)
{
    //char inputBuffer[MAX_LINE];
    int length, /* # of characters in the command line */
    i,      /* loop index for accessing inputBuffer array */
    start,  /* index where beginning of next command parameter is */
    ct;     /* index of where to place the next parameter into args[] */
    int add = 1;
    ct = 0;

    /* read what the user enters on the command line */
    length = read(STDIN_FILENO, inputBuffer, MAX_LINE);  


        printf("%i",length);
    start = -1;
    if (length == 0)
        exit(0);            /* ^d was entered, end of user command stream */
    if (length < 0){
        perror("error reading the commanddddddddd");
        exit(-1);           /* terminate with error code of -1 */
    }
}



int main(void)
{
    char inputBuffer[MAX_LINE]; /* buffer to hold the command entered */
    int background;             /* equals 1 if a command is followed by '&' */
    char *args[MAX_LINE/2+1];/* command line (of 80) has max of 40 arguments */
    FILE *inFile = fopen("pateljay.history", "r");



    if (inFile != NULL) {
        int count = 0;
        char line[MAX_LINE];
        while (fgets(line,sizeof line, inFile) != NULL) {
            string[count] = strdup(line);
            //string[count][strlen(line)] = '\n';
            //string[count][strlen(line) + 1] = '\0';
            printf("%s", string[count]);
            count++;
            stringSize++;
        }


            p = count % 10;
            recent = abs(p - 1);

    }   

    fclose(inFile); 

    /* set up the signal handler */
    struct sigaction handler;
    handler.sa_handler = handle_SIGINT;
    sigaction(SIGINT, &handler, NULL);

    while (1) {/* Program terminates normally inside setup */


        background = 0;
        printf("COMMAND->");

        fflush(0);

        setup(inputBuffer, args, &background);/* get next command */
    }
}

So, when ctrl + c is entered, it should catch the signal and process it. As soon as he returns to the main one, he goes into the setup and completely skips the read function and makes the length equal to -1. This, in turn, leads to errors in the program. I think the code inside handle_SIGINT doesn't matter as it is now. Does anyone know why it skips the read function in setup?

Answer 1

read , . SIGINT. . , ​​ read return -1 errno EINTR. , read :

   do {
        length = read(STDIN_FILENO, inputBuffer, MAX_LINE);
   } while (length == -1 && errno == EINTR);

Answer 2

int:

void handle_sigint(int signum) {}