Am 10.01.2018 um 00:22 schrieb Ari Sundholm:
> Busybox dd has a difference in behavior compared to coreutils dd
> in the case where the block count has been given and the last block
> can only partially be written (usually due to ENOSPC):
>
> $ dd if=/dev/zero of=foo bs=100M count=8; echo $?; rm foo
> dd: error writing 'foo': No space left on device
> 8+0 records in
> 7+0 records out
> 805220352 bytes (805 MB, 768 MiB) copied, 0.405782 s, 2.0 GB/s
> 1
> $ busybox dd if=/dev/zero of=foo bs=100M count=8; echo $?; rm foo
> 8+0 records in
> 7+1 records out
> 0
> $ df -h .
> Filesystem Size Used Avail Use% Mounted on
> tmpfs 768M 8.0K 768M 1% [redacted]
> $
>
> This breaks scripts which rely on busybox dd giving an exit value
> indicating failure when writing data fails.
>
> The solution is to error out when the block that was just read (be
> it full or partial) couldn't be written out in full, just as coreutils
> dd does.
>
> Signed-off-by: Ari Sundholm <[email protected]>
> ---
> coreutils/dd.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/coreutils/dd.c b/coreutils/dd.c
> index d302f35..6221ebe 100644
> --- a/coreutils/dd.c
> +++ b/coreutils/dd.c
> @@ -195,13 +195,15 @@ static bool write_and_stats(const void *buf, size_t
> len, size_t obs,
> ssize_t n = full_write_or_warn(buf, len, filename);
> if (n < 0)
> return 1;
> - if ((size_t)n == obs)
> - G.out_full++;
> - else if (n) /* > 0 */
> - G.out_part++;
> #if ENABLE_FEATURE_DD_THIRD_STATUS_LINE
> G.total_bytes += n;
> #endif
> + if ((size_t)n == obs)
> + G.out_full++;
> + else if ((size_t)n == len)
> + G.out_part++;
> + else /* if ((size_t)n != len) */
even here, G.out_part should be increased, at least if (n > 0), maybe
like this:
if ((size_t)n == obs)
G.out_full++;
else {
G.out_part++;
/* doesn't work when len == 0! */
if ((size_t)n != len)
return 1;
}
return 0;
> + return 1;
> return 0;
> }--
Stefan Seyfried
"For a successful technology, reality must take precedence over
public relations, for nature cannot be fooled." -- Richard Feynman
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