Problem with cat

Grant Edwards grant.b.edwards at gmail.com
Mon Mar 13 18:12:19 UTC 2017


On 2017-03-13, Grant Edwards <grant.b.edwards at gmail.com> wrote:

> After upgrading to a new version of busybox (1.25.1), I now have an
> odd problem with 'cat'.  When stdout is a file, it _appears_ to be
> doing a seek to the beginning of the output file between input files.
[...]
>   # ls -l
>   total 12
>   -rw-r--r--    1 root     root            29 Mar 13 17:44 d1
>   -rw-r--r--    1 root     root            29 Mar 13 17:44 d2
>   -rw-r--r--    1 root     root            29 Mar 13 17:44 d3
>
>   # cat d1 d2 d3
>   Mon Mar 13 17:44:35 UTC 2017
>   Mon Mar 13 17:44:40 UTC 2017
>   Mon Mar 13 17:44:43 UTC 2017
>
>   # cat d1 d2 d3 >foo
>
>   # ls -l
>   total 16
>   -rw-r--r--    1 root     root            29 Mar 13 17:44 d1
>   -rw-r--r--    1 root     root            29 Mar 13 17:44 d2
>   -rw-r--r--    1 root     root            29 Mar 13 17:44 d3
>   -rw-r--r--    1 root     root            29 Mar 13 17:46 foo
>
>   # cat foo
>   Mon Mar 13 17:44:43 UTC 2017

The failure is happening w/ busybox 1.25.1 on an ARM9 running kernel
2.6.33.7.

The same version of busybox on an AMD64 running kernel 4.4.39 works
fine.

The strace output for the read/sendfile operations looks identical
between the two, so it sort of looks like a kernel problem...

-- 
Grant Edwards               grant.b.edwards        Yow! I'm not available
                                  at               for comment..
                              gmail.com            



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