Re: Man page bugs?

[WANG Cong <xiyou.wangcong-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On Thu, Jan 31, 2008 at 02:28:58PM +0100, Jens Axboe wrote:
>On Thu, Jan 31 2008, Michael Kerrisk wrote:
>> 
>> 
>> Jens Axboe wrote:
>> > On Thu, Jan 31 2008, Michael Kerrisk wrote:
>> >> Hi Cong,
>> >>
>> >> WANG Cong wrote:
>> >>> Hi, Michael and list!
>> >>>
>> >>> I found two problems in the man pages. The first one should
>> >>> be a bug. It is that the type of the 2nd and 4th arguments
>> >>> of splice(2) is wrong. The current prototype of splice(2)
>> >>> in current man page is:
>> >>>
>> >>>        long splice(int fd_in, off_t *off_in, int fd_out,
>> >>>                    off_t *off_out, size_t len, unsigned int flags);
>> >>>
>> >>> However, they should be 'loff_t' instead of 'off_t'. If we
>> >>> use 'off_t', gcc will generate a warning. Patch is in the end
>> >>> of this email and it's against 2.76 release. ;)
>> >> Thanks for spotting that.  Fixed as you suggest, for man-pages-2.77.
>> >>
>> >>> The second one is a bit confused. The example given in tee(2)
>> >>> even can not run normally. I got this error:
>> >>>
>> >>> $ ./example bar.txt
>> >>> tee: Invalid argument
>> >>>
>> >>> I looked at tee(2), it is said that:
>> >>>
>> >>> EINVAL fd_in  or  fd_out  does not refer to a pipe; or fd_in and fd_out
>> >>>        refer to the same pipe.
>> >>>
>> >>> So the first two arguments of tee(2) in the example is wrong,
>> >>> since neither STDIN_FILENO nor STDOUT_FILENO refers to a pipe.
>> >>> But I am not so sure, because I am new to tee(2). ;) If you can
>> >>> comfirm this is really a bug, I can send a patch to fix this too.
>> >>>
>> >>> I have checked the newest release of man pages and my kernel version
>> >>> is 2.6.21-1.3194.fc7. Did I miss something obvious?
>> >> I'm not sure.  Perhaps Jens, the implementer of tee(2) can provide a little
>> >> help.  Jens, what's an example of a command line for running the example
>> >> program in the tee.2 man page?
>> > 
>> > It's not a bug, it should be run as:
>> > 
>> > $  echo hello | ./example output_file | cat
>> > 
>> > so that both stdin and stdout are pipes, as described in the man page.
>> > The man page is correct.


I think man page should mention about this usage.

>> 
>> Hi jens,
>> 
>> Yes, I guessed you probably should run it like that.  And it does produce
>> the expected output on stdout.  However, the command then blocks, and if
>> one types control-C, the output_file is empty.  How should this program be
>> terminated so that something does end up in the output_file?
>
>See ktee.c from the splice sample repo, it works correctly:
>
>axboe@carl:~/git/splice> echo hello | ./ktee outfile | cat
>hello
>axboe@carl:~/git/splice> cat outfile 
>hello
>
>I don't have the tee(2) man page here so can't verify, but try and
>compare them!
>

I have the same problem here with what Michael mentioned.
But my output file is *not* empty. Shown below:

$ echo hello | ./tee fooo.txt | cat
hello
	<=== here blocked, type ctrl+c, exit
$ cat fooo.txt 
hello

My kernel version is 2.6.21-1.3194.fc7.

Thank you!