/*
 * Copyright 2008, Axel Dörfler, axeld@pinc-software.de.
 * Distributed under the terms of the MIT License.
 */


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


extern const char *__progname;


int
main(int argc, char **argv)
{
        if (argc < 3) {
                fprintf(stderr, "usage: %s <file> <size>\n", __progname);
                return 1;
        }

        struct stat st;
        if (stat(argv[1], &st) != 0) {
                fprintf(stderr, "%s: cannot stat file \"%s\": %s\n", __progname,
                        argv[1], strerror(errno));
                return 1;
        }

        off_t newSize = strtoll(argv[2], NULL, 0);

        printf("size   %10Ld\n", st.st_size);
        printf("wanted %10Ld\n", newSize);
        printf("Do you really want to truncate the file [y/N]? ");
        fflush(stdout);

        char yes[10];
        if (fgets(yes, sizeof(yes), stdin) == NULL || tolower(yes[0]) != 'y')
                return 0;

        if (truncate(argv[1], newSize) != 0) {
                fprintf(stderr, "%s: cannot truncate file \"%s\": %s\n", __progname,
                        argv[1], strerror(errno));
                return 1;
        }

        int fd = open(argv[1], O_RDONLY);
        if (fd < 0) {
                fprintf(stderr, "%s: could open the file read-only \"%s\": %s\n",
                        __progname, argv[1], strerror(errno));
                return 1;
        }
        if (ftruncate(fd, newSize) == 0 || errno != EINVAL) {
                fprintf(stderr, "%s: could truncate a file opened read-only \"%s\": %s\n",
                        __progname, argv[1], strerror(errno));
                close(fd);
                return 1;
        }
        close(fd);

        return 0;
}