/**
 *  Copyright (C) 2012 NAKAMURA Minoru <nminoru@nminoru.jp>
 *
 *  gcc -Wall -g -D _GNU_SOURCE hole-punch.c -o hole-punch
 */
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>

#include <fcntl.h>
#include <linux/falloc.h>



int main(int argc, char **argv)
{
    if (argc != 4) {
        fprintf(stderr, "Syntax: %s filename offset length\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    int fd;
    if ((fd = open(argv[1], O_RDWR)) < 0) {
        fprintf(stderr, "Cannot open %s\n", argv[1]);
        exit(EXIT_FAILURE);
    }

    unsigned long offset, len;
    offset = atol(argv[2]);
    len    = atol(argv[3]);

    if (fallocate(fd, FALLOC_FL_KEEP_SIZE|FALLOC_FL_PUNCH_HOLE, offset, len)) {
        int eno = errno;
        fprintf(stderr, "Failure: fallocate(fd, FALLOC_FL_PUNCH_HOLE, ) errno=%s(%d)\n",
                strerror(eno), eno);
        exit(EXIT_FAILURE);
    }

    close(fd);

    exit(EXIT_SUCCESS);

    return 0;
}