Administrace komentářů

Ahoj,

mam za ukol napsat daemona v C jako takovou nahradu za syslog.

Daemon přijímá data z pojmenované roury, zapisovat do tohoto souboru smí kdokoliv. Prvním parametrem daemona je název souboru, do kterého bude zapisovat události ve tvaru

time caller: message

A dale vytvorit knihovnu s funkcí pro zápis do této roury. dalším parametrem daemona je interval, ve kterém daemon zapisuje vlastní statistiku (počet obdržených zpráv) do syslogu.

Daemon jsem napsal pomoci fce select(), ale nemuzu odstranit chybu, ktera spociva v ukonceni programu pote, co si precte prvni zpravu z roury a korektne ji zapise do zadaneho logu.

V nasledujicim prubehu WHILE funkce select vrati hodnotu vetsi nez nula, jakoby dosla dalsi zprava, ale funkce read vrati nulu. Zajimalo by me, kde je chyba. Je to nekde v souboru s rourou, nebo v samotnem spatnem pouziti select ?

Kod daemona:

/*
 
#define DEFAULT_INTERVAL 2
#define SIZE 256

char* get_current_time() {

    
        time_t current_time;
        char* c_time_string;
        int j;
        current_time = time(NULL); /* Obtain current time as seconds elapsed since the Epoch. */
 
        if (current_time == ((time_t)-1)) {
            
                (void) fprintf(stderr, "Failure to compute the current time.");
                exit(EXIT_FAILURE);
        }
                       
        c_time_string = ctime(¤t_time);  /* Convert to local time format. */
                                               
        for ( j = 0; c_time_string[j] != '\n'; j++)  /*Get rid EOL*/
                                ;                          
        c_time_string[j] = '\0';
 
        if (c_time_string == NULL) {
            
                (void) fprintf(stderr, "Failure to convert the current time.");
                exit(EXIT_FAILURE);
        }
        
        return c_time_string;   
}

void print_help() {

        printf("Programme must be run with with 2 arguments:\n"
            "argv[1] is a name of the file which the daemon wil be writting in\n"
            "argv[2] is an interval the daemon will be sending logs into syslog\n");
}

int main(int argc, char *argv[]) {

        if (argc != 3) {
    
                print_help();
                exit(1);
        }
        
        int c;
        while((c = getopt(argc, argv, "h")) != -1) {

                switch (c) {

                case 'h':
                        print_help();
                        break;
                        
                case '?':
                        printf("try -h for help");
                        break;
                default:
                    break;
                }

        }
    

        FILE *fw;
        int fp;
        char buf[SIZE];
    char *linesep;
        int line, i, count; 
        buf[0] = '\0'; // in case there is nothing to read
        buf[SIZE] = '\0'; // guarentee a end-of-line
        fd_set readfds;
        struct timeval timeout;
        int r;
        int interval = atoi(argv[2]);
    openlog ("exampleprog", LOG_CONS | LOG_PID | LOG_NDELAY, LOG_LOCAL1);
        
    fprintf(stderr, "Daemonizing...\n");    
    //daemon(0,0);

    unlink("/tmp/pb173_syslog");
        mkfifo("/tmp/pb173_syslog", S_IWUSR | S_IRUSR | S_IRGRP | S_IROTH);
    
        fp = open("/tmp/pb173_syslog", O_RDONLY | O_NONBLOCK);

        if(fp == -1) {
        syslog (LOG_CRIT, "Could not open the pipe: %s\n", strerror(errno));
                exit(1);
        }

    fw = fopen(argv[1], "a+");

        if(fw == NULL) {
        openlog ("exampleprog", LOG_CONS | LOG_PID | LOG_NDELAY, LOG_LOCAL1);
        syslog (LOG_CRIT, "Error openning logfile : %s\n", strerror(errno));
                exit(1);
        }

        
        timeout.tv_sec = interval; 
        timeout.tv_usec = 0;
        count = 0;
       
    line = 0; 
    r = 0;
        while(1) {        
        FD_ZERO(&readfds);
        FD_SET(fp,&readfds);
                r = select(fp+1, &readfds, NULL, NULL, &timeout);
        if (r == -1) {
            openlog ("daemon", LOG_CONS | LOG_PID | LOG_NDELAY, LOG_LOCAL1);
            syslog (LOG_CRIT, "Error openning logfile : %s\n", strerror(errno));
            close(fp);
            fclose(fw);
            exit(1);
        }
            if (r == 0) {
            timeout.tv_sec = interval;
            timeout.tv_usec = 0;
            setlogmask (LOG_UPTO (LOG_NOTICE));    
                        openlog ("daemon", LOG_CONS | LOG_PID | LOG_NDELAY, LOG_LOCAL1);
                        syslog (LOG_NOTICE, "Number of received messages: %d\n", count ); 
                        closelog ();        
        } else {
            line += (r = read(fp, buf+line, SIZE-line-1));
            if (r == 0) {
                close(fp);
                fclose(fw);

                exit(EXIT_SUCCESS);
            }
            buf[line] = '\0';

            if (line && (linesep = strstr(buf, "\n"))) { 
                *linesep = '\0';
                char *caller;
                int callerLength;
                char *message;
                caller = strtok(buf, "^");
                callerLength = strlen(caller);
                message = caller + callerLength + 1;
                fprintf(fw, "%s %s: %s\n", get_current_time(), caller, message);
                fflush(fw);
                memmove(buf, linesep + 1, (line = strlen(linesep + 1)) + 1);                
                count++;
                    }
                }       
        }
        
        close(fp);
        fclose(fw);

        exit(EXIT_SUCCESS);
}

A kod funkce, ktera zapisuje do roury:

int sl_log(const char *caller, const char* message) {
    
    int fp;
    fp = open("/tmp/pb173_syslog", O_WRONLY);
    char *msg;

    if (fp == -1) {
        perror("Could not open the pipe\n");
        exit(1);
    }
    
    asprintf(&msg, "%s^%s\n", caller, message);
    write(fp, msg, strlen(msg));
    free(msg);
    close(fp);
    return 0;
}