Re: [Groff] new groff_differences.man

[Ralph Corderoy]

Hi Clarke,

> Unix doesn't care and never did that I am aware of.  As long as the
> total length was 14 characters or less it didn't matter.  You could
> have one character, a dot, and 12 suffix characters or 12 characters,
> a dot, and a one-character suffix, and it was equally happy.

The dot character isn't actually special as far as Unix is concerned.
Unlike DOS you don't need a dot, or you can have many:
`..............'.  The directory entries `.' and `..' are special
though as the kernel knows about them when making a directory.

> Even 14 for the limit makes me wonder where that limit came from
> since it is not an integer multiple of 2.

It's 2^4 - 2.  A directory was just a list of two-byte inode numbers
and the associated 14-character filename.  You used to be able to treat
a directory as a file in many cases and still can on older machines.

    $ od -c . | head -3
    0000000   \0 023   .  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0
    0000020   \0 002   .   .  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0
    0000040   \0 024   .   p   r   o   f   i   l   e  \0  \0  \0  \0  \0  \0

Cheers,


Ralph.