man page improvements

[NAGATA Shinya]

Hi,

I suggest improvements of man page description.


1. about bsf
>       fsf    Forward space count files.  The tape is positioned on the first
>              block of the next file.
>       bsf    Backward space count files.  The tape is positioned on the first
>              block of the next file.

In this description, both fsf and bsf seem to move to the *first* block of the 
*next* file.
But bsf backs to EOF and stop at between *last* block of *previous* file and 
EOF.

Tape structure and stop positions as I understand:
~--+-----+-----+-----+-----+-----+-----+-----+-~
  file 1 data blocks | EOF | file 2 data blocks
~--+-----+-----+-----+-----+-----+-----+-----+-~
fsf
 ------------------------->^ stops here
  the first block of next file (file 2)
bsf
          stops here ^<-------------------------
  the last block of previous file (file 1)

I suggest that following description is better:
>       bsf    Backward space count files.  The tape is positioned on the last
>              block of the previous file.


2. about bsfm
>       fsfm   Forward space count file marks.  The tape is positioned  on  the
>              beginning-of-the-tape side of the file mark.
>       bsfm   Backward  space count file marks.  The tape is positioned on the
>              beginning-of-the-tape side of the file mark.

In this description, both fsfm and bsfm seem to move to the 
*beginning-of-the-tape side* of the file mark.
But bsfm backs to EOF and reposition to the *end-of-the-tape side* of the file 
mark.

Tape structure and stop positions as I understand:
~--+-----+-----+-----+-----+-----+-----+-----+-~
  file 1 data blocks | EOF | file 2 data blocks
~--+-----+-----+-----+-----+-----+-----+-----+-~
fsfm
     ----------------------> comes here
                     ^<----  and turns back, stops here
  the beginning-of-the-tape side of the file mark
bsfm
         comes here  <--------------------------
                     ----->^ and turns back, stops here
  the end-of-the-tape-side of the file mark

Also 'man 4 st' says
https://man7.org/linux/man-pages/man4/st.4.html
> MTBSFM Backward space over mt_count filemarks.  Reposition the
>        tape to the EOT side of the last filemark.

I suggest that following description is better:
>       bsfm   Backward  space count file marks.  The tape is positioned on the
>              end-of-the-tape-side of the file mark.


This report may from my incomplete understanding.
I read 'man mt,' operate a tape drive with mt command and 'mt status,'
on both of cpio (at Ubuntu) and mt-st (Cent OS).
I don't have a way to know the physical position of tape drive header on a tape.
I am sorry if this report is not correct from my misunderstanding.

Thanks,
NAGATA Shinya