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
