Administrace komentářů

Chyb je tam hned niekolko:

• nekontrolujes argc
• netestujes argv[1] na prekrocenie LENGTH
• pri detekcii chyby program neskonci, ale pokracuje dalej
• premenna string je uplne zbytocna - zrusit (nahradit vsade za file_memory)
• vo while neflushujes stdout buffer (robi to napr. \n)
• je tam este potencial na race condition, o ktorej su to skoro vsetky ostatne komentare, takze by nemuselo byt od veci pred zapisom ziskat file lock a po zapise ho uvolnit
• file_memory je zbytocne void *, ked mmap explicitne pretypovavas na char *

Vysledok? Nieco taketo:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/file.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <fcntl.h>

#define LENGTH 0x100

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

        int fd;
        char *file_memory;
        
        if(argc != 2 || strlen(argv[1]) > LENGTH) {
        	printf("Usage: ...\n");
        	return 1;
        }
        if ((fd = open("./mapped_file", O_CREAT | O_RDWR,
                S_IRUSR | S_IWUSR)) == -1) {
                perror("open failed");
                return 1;
        }
        if(ftruncate(fd, LENGTH + 1) < 0) {
        	perror("ftruncate:");
        	return 1;
        }

        file_memory = (char *)mmap(NULL, LENGTH, PROT_WRITE, MAP_SHARED, fd, 0);
        
        if (file_memory == MAP_FAILED) {
            
                perror("mmap failed");
                return 1;
        }
        if(flock(fd, LOCK_EX) < 0) {
        	perror("flock lock");
        	return 1;
        }
        sprintf(file_memory, "%s", argv[1]);
        if(flock(fd, LOCK_UN) < 0) {
        	perror("flock unlock");
        	return 1;
        }
        while(1){
                printf("%s\n", file_memory);
                sleep(2);
        }
        munmap(file_memory, LENGTH);
        return (EXIT_SUCCESS);
}