4-4

#include <unistd.h>
#include <sys/wait.h>
#include <stdlib.h>
#include <fcntl.h>
#include <stdio.h>
#include <sys/stat.h>
#include <limits.h>
#include <inttypes.h>

int
main(int argc, char *argv[])
{
    int fl = open(argv[1], O_RDWR);
    long long num, min = LLONG_MAX;
    int curofst = 0, minofst;
    while (read(fl, &num, sizeof(num)) >= 0) {
        if (num < min) {
            min = num;
            minofst = curofst;
        }
        curofst += sizeof(num);
    }
    if (min == LLONG_MIN) {
        min = 0;
    } else {
        min = -min;
    }
    lseek(fl, SEEK_SET, minofst);
    write(fl, &min, sizeof(min));
    close(fl);
    return 0;
}