segmentation fault in reading /proc/pid/maps

Question

I'm trying to read maps line by line, but I get the error core segmentation fault error... Can anyone give me some advice on my code? I'm using 3.13.0-32-generic

int main()
{
    char buf[512];
    FILE *f;
    sprintf(buf, "/proc/%d/maps", getpid());
    f = fopen(buf, "rt");
    while (fgets(buf, 512, f)) {
        unsigned int from, to, pgoff, major, minor;
        unsigned long ino;
        char flags[4];
        int ret = sscanf(buf, "%x-%x %c%c%c%c %x %x:%x %lu ", &from, &to, flags[0],flags[1],flags[2],flags[3], &pgoff, &major, &minor,ino);
            if (ret != 10)
            break;
    }
}

Answer 1

You need to pass pointers to the members of the flags array instead of passing them directly, the same applies to the ino argument:

sscanf(buf, "%x-%x %c%c%c%c %x %x:%x %lu ", &from, &to,
    &flags[0], &flags[1], &flags[2], &flags[3],
    &pgoff, &major, &minor, &ino);

Alternatively, scan all characters at once:

sscanf(buf, "%x-%x %4c %x %x:%x %lu ", &from, &to,
    flags, &pgoff, &major, &minor, &ino);

Notice the missing & before flags as the array is automatically converted into a pointer to its first element when passed to a function.

Answer 2

In the scanf call replace

flags[x]

by

&flags[x]

same goes for ino .