open_read.c

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

inline int get_fsize(int fd) {
	struct stat sb;
	int err;
	err = fstat(fd, &sb);
	if (err) {
		fprintf(stderr, "fstat error! [%s]\n", strerror(errno));
		return -1;
	}
	return sb.st_size;
}

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

	int fd;
	char *path, *buf;
	int i, cnt = 0;
	int fsize;
	int length;

	if (argc < 2) {
		fprintf(stderr, "require file path.\n");
		return -1;
	}
	path = argv[1];

	fd = open(path, O_RDONLY);
	fsize = get_fsize(fd);
	if (fsize < 0) {
		return -1;
	}
	buf = (char*)malloc(fsize);
	length = read(fd, buf, fsize);
	if (length < fsize) {
		fprintf(stderr, "read error! [%d]\n", length);
	}

	for (i=0; i<fsize; i++) {
		if (buf[i] == 0x00) cnt++;
	}

	free(buf);
	close(fd);

	printf("%s: size=%d cnt=%d\n", path, fsize, cnt);

	return 0;
}