Re: [PATCH v2 1/2] t: add a test helper to truncate files

> In a future commit, we're going to work with some large files which will
> be at least 4 GiB in size.  To take advantage of the sparseness
> functionality on most Unix systems and avoid running the system out of
> disk, it would be convenient to use truncate(2) to simply create a
> sparse file of sufficient size.
>
> However, the GNU truncate(1) utility isn't portable, so let's write a
> tiny test helper that does the work for us.
>
> Signed-off-by: brian m. carlson <bk2204@github.com>
> ---
> diff --git a/t/helper/test-truncate.c b/t/helper/test-truncate.c
> @@ -0,0 +1,27 @@
> +int cmd__truncate(int argc, const char **argv)
> +{
> +       char *p = NULL;
> +       uintmax_t sz = 0;
> +       int fd = -1;
> +
> +       if (argc != 3)
> +               die("expected filename and size");
> +
> +       sz = strtoumax(argv[2], &p, 0);
> +       if (*p)
> +               die("invalid size");

> +       fd = open(argv[1], O_WRONLY | O_CREAT, 0600);
> +       if (fd < 0)
> +               die_errno("failed to open file %s", argv[1]);
> +
> +       if (ftruncate(fd, (off_t) sz) < 0)
> +               die_errno("failed to truncate file");
> +       return 0;
> +}