Re: file signature

[Richard]

"Bill Cunningham" <nospam@nspam.i nvalidwrites:

I can't use stdc to write a file signature for a file format can I?
Wouldn't I have to get into the sys calls and maybe even kernel internals to
do this with lynx. I am going to write a parser soon. But I want to parser
to have a unique signature in it's header somewhere. 0x7f is I believe the
signature for linux. I will write a 128 unique number generator in C with
linux to get the number so it will not conflict with other file types like
adobe's .pdf and so on. Can anyone suggest any source code to create a file
signature and what else I might need to do?
>
Bill

By stdc do you mean "standard c" Bill?

I think you should ask in c.l.c : they are always willing to help people
with their parsers and 128 unique number generators there!

Enjoy!

9/10

Crosspost & Followup-To: comp.lang.c

(ps not bad - almost as good as the one where you were telling the lads
in linux development how you were about to write a device driver!)

[Nick Keighley]

Re: file signature

On 25 Sep, 01:56, Richard<rgr...@ gmail.comwrote:

"Bill Cunningham" <nos...@nspam.i nvalidwrites:

    I can't use stdc to write a file signature for a file format can I?

what's a file signature? Do you want a way of deducing the file type
by reading some sort of meta-data? comp.programmin g is probably
the place to go. This sort of file signature stuff is highly OS
dependent.

Windows: use the file extension
old Mac OS: stick something in the resource fork of the file
(yes you would need "kernel" calls for that!)
unix: uses something called "magic" which is essentially
stuff at the front of the file

Wouldn't I have to get into the sys calls and maybe even kernel internals to
do this with lynx.

lynx?
wiki: "The LynxOS RTOS is a Unix-like real-time operating system from
LynuxWorks (formerly "Lynx Real-Time Systems"). Sometimes known as the
Lynx Operating System, LynxOS features full POSIX conformance and,
more recently,
Linux compatibility. LynxOS is mostly used in real-time embedded
systems, in applications for avionics, aerospace, the military,
industrial process
control and telecommunicati ons."

I bet you didn't mean that

I am going to write a parser soon.

<giggle>

But I want to parser
to have a unique signature in it's header somewhere. 0x7f is I believe the
signature for linux.

no

I will write a 128 unique number generator in C with
linux to get the number so it will not conflict with other file types like
adobe's .pdf and so on. Can anyone suggest any source code to create a file
signature and what else I might need to do?

the simplest think to do on Unix-like system is to put
some fairly simple text on the first line and hide it
in a comment. Suppose I was posting something that used ;
as a comment I could tag my file like this

;!/bin/nil

The perl programming langauge often tags its programs with

#!/opt/perl5/perl

the ! sequence tells the shell (the Operating System in effect)
where to find the correct reader for that file type. Ask on a Unix ng
for details.


--
Nick Keighley

[Richard]

Re: file signature

Nick Keighley <nick_keighley_ nospam@hotmail. comwrites:

On 25 Sep, 01:56, Richard<rgr...@ gmail.comwrote:

>"Bill Cunningham" <nos...@nspam.i nvalidwrites:

>

    I can't use stdc to write a file signature for a file format can I?

>
what's a file signature? Do you want a way of deducing the file type
by reading some sort of meta-data? comp.programmin g is probably
the place to go. This sort of file signature stuff is highly OS
dependent.

You did notice that I somewhat mischievously cross posted this from the
linux application development group didn't you?

>

I am going to write a parser soon.

>
<giggle>

And that's why ....

[Richard Heathfield]

Re: file signature

Nick Keighley said:

On 25 Sep, 01:56, Richard<rgr...@ gmail.comwrote:

>"Bill Cunningham" <nos...@nspam.i nvalidwrites:

>

I can't use stdc to write a file signature for a file format can I?

>
what's a file signature? Do you want a way of deducing the file type
by reading some sort of meta-data? comp.programmin g is probably
the place to go. This sort of file signature stuff is highly OS
dependent.
>
Windows: use the file extension

No, don't do that.

I once had to write a program that could tell the difference between PDF
files and PDF files, because Adobe's johnny-come-lately "Portable Document
Format" extension clashed horribly with a venerable and ancient vendor's
"Program Description File" extension. The customer organisation then
issued my program as the "official" PDF association, and my program
performed the relevant action for dealing with the PDF (either starting
the relevant application or aborting if the file format were not
recognised), depending on whether it was a PDF, a PDF, or of course a PDF.

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

[Bill Cunningham]

Re: file signature


"Nick Keighley" <nick_keighley_ nospam@hotmail. comwrote in message
news:e5e3e123-01df-4771-92fa-eeff996a8752@y2 1g2000hsf.googl egroups.com...
On 25 Sep, 01:56, Richard<rgr...@ gmail.comwrote:

"Bill Cunningham" <nos...@nspam.i nvalidwrites:

I can't use stdc to write a file signature for a file format can I?

what's a file signature? Do you want a way of deducing the file type
by reading some sort of meta-data? comp.programmin g is probably
the place to go. This sort of file signature stuff is highly OS
dependent.

I believe I want to insert a magic number in an ELF header. Did I post
this here? I remember comp.prog and col groups I posted it. This is here by
mistake.

Bill

[Keith Thompson]

Re: file signature

"Bill Cunningham" <nospam@nspam.i nvalidwrites:

"Nick Keighley" <nick_keighley_ nospam@hotmail. comwrote in message
news:e5e3e123-01df-4771-92fa-eeff996a8752@y2 1g2000hsf.googl egroups.com...

On 25 Sep, 01:56, Richard<rgr...@ gmail.comwrote:

"Bill Cunningham" <nos...@nspam.i nvalidwrites:

I can't use stdc to write a file signature for a file format can I?

what's a file signature? Do you want a way of deducing the file type
by reading some sort of meta-data? comp.programmin g is probably
the place to go. This sort of file signature stuff is highly OS
dependent.

>
I believe I want to insert a magic number in an ELF header. Did I post
this here? I remember comp.prog and col groups I posted it. This is here by
mistake.

You posted in comp.os.linux.d evelopment.syst em. This is here because
Richard Nolastname deliberately cross-posted and redirected followups
to comp.lang.c.

But as long as it's here, judging by the way you've struggled with the
most elementary C programs, I suspect what you're attempting is beyond
your abilities.

--
Keith Thompson (The_Other_Keit h) kst-u@mib.org <http://www.ghoti.net/~kst>
Nokia
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"

[Bill Cunningham]

Re: file signature


"Keith Thompson" <kst-u@mib.orgwrote in message
news:lnej374xld .fsf@nuthaus.mi b.org...

But as long as it's here, judging by the way you've struggled with the
most elementary C programs, I suspect what you're attempting is beyond
your abilities.

Your quite probably right. I know you are without some kind of tutorial.
elf.h used data types called uint_t for unsigned ints. I hope it is
understood what I am wanting to attempt.

Bill

[Nick Keighley]

Re: file signature

On 25 Sep, 16:53, Richard Heathfield <r...@see.sig.i nvalidwrote:

Nick Keighleysaid:
>

On 25 Sep, 01:56, Richard<rgr...@ gmail.comwrote:

"Bill Cunningham" <nos...@nspam.i nvalidwrites:

>

I can't use stdc to write a file signature for a file format can I?

>

what's a file signature? Do you want a way of deducing the file type
by reading some sort of meta-data? comp.programmin g is probably
the place to go. This sort of file signature stuff is highly OS
dependent.

>

Windows: use the file extension

>
No, don't do that.

I rather meant- that was often what happened. I'm not particularly
fond of it.

--
Nick Keighley

[Keith Thompson]

Re: file signature

"Bill Cunningham" <nospam@nspam.i nvalidwrites:

"Keith Thompson" <kst-u@mib.orgwrote in message
news:lnej374xld .fsf@nuthaus.mi b.org...

>But as long as it's here, judging by the way you've struggled with the
>most elementary C programs, I suspect what you're attempting is beyond
>your abilities.

>
Your quite probably right. I know you are without some kind of tutorial.
elf.h used data types called uint_t for unsigned ints.

No, elf.h (at least on my system) doesn't use anything called uint_t.
It does use uint16_t, uint32_t, and uint64_t, all of which are
declared in the standard header <stdint.h>.

I hope it is
understood what I am wanting to attempt.

I have no idea what you're attempting.

--
Keith Thompson (The_Other_Keit h) kst-u@mib.org <http://www.ghoti.net/~kst>
Nokia
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"