Re: [9fans] a question of file and the history of magic

[erik quanstrom <quanstro@quanstro.net>]

> This addition helped my scripts become a little more streamlined, but
> of course puts in an additional entry into the source file I need to
> track.  As file name extensions don't always work across all sorts of
> systems, many still hamstrung by 8.3, what is the preferred or
> recommend mechanism for checking file types the Plan 9 way since we no
> longer have the System V magic?

i'm pretty confused by what you're saying here.  why doesn't file(1) work?
are you saying there's something wrong with editing the source as opposed
to to editing a configuration file?

either way your system is equally non-standard.  in either event,
submitting a patch and having it accepted is the only way around this.

> In a sense, a modified xd(1) that has an option for a restricted range
> of byte sequences would work.  That would at least provide a fast seek
> into a file that can be pipelined into any other command sequence--no
> need to dump the whole file when you just need to the first four
> bytes, but then it just gets to the point of having a magic file.

why would xd need modification?  how about

	dd -if $infile -bs $nbytes -count 1 | xd

there are no restrictions placed by dd on $nbytes.  it could be
4 or 99132 or whatever.  dd's -iseek option similarly can specify
any offset.

- erik