how to determine a file is ASCII or binary?

[Sunner Sun]

Hi, all

Since the OS look both ASCII and binary file as a sequence of bytes, is
there any way to determine the file type except to judge the extension?

Thank you!

[Peter Pichler]

"Dan Pop" <Da*****@cern.c h> wrote in message
news:c5******** **@sunnews.cern .ch...

In <Hw********@cwi .nl> "Dik T. Winter" <Di********@cwi .nl> writes:

There has been an example of an executable which consisted only
of bytes in the printable ASCII range.

ALL my Perl and /bin/sh executables consist only of bytes in the
printable ASCII range ;-)

It is arguable whether they qualify as "executable s". Dik was probably
talking about EICAR or something similar. Look up EICAR in Google.

Peter

[Dik T. Winter]

In article <40**********@m k-nntp-2.news.uk.tisca li.com> "Peter Pichler" <pi*****@pobox. sk> writes:

"Dan Pop" <Da*****@cern.c h> wrote in message
news:c5******** **@sunnews.cern .ch...

In <Hw********@cwi .nl> "Dik T. Winter" <Di********@cwi .nl> writes:

There has been an example of an executable which consisted only
of bytes in the printable ASCII range.

ALL my Perl and /bin/sh executables consist only of bytes in the
printable ASCII range ;-)

It is arguable whether they qualify as "executable s". Dik was probably
talking about EICAR or something similar. Look up EICAR in Google.

Nope, much older. It is an old story about a workstation where a rm -rf /
in the works was aborted, but not in time to lose almost all object files
(/bin /usr/bin). Luckily there was a window open with a shell and a
window with a texteditor (vi). On a similar machine an executable was
produced that consisted of ASCII characters only. This was entered in
the text editor, a file was written, in the shell a chmod performed
(built-in), and so a start of recovery was found.

--
dik t. winter, cwi, kruislaan 413, 1098 sj amsterdam, nederland, [phone]
home: bovenover 215, 1025 jn amsterdam, nederland; http://www.cwi.nl/~dik/

[Dan Pop]

In <40**********@m k-nntp-2.news.uk.tisca li.com> "Peter Pichler" <pi*****@pobox. sk> writes:

"Dan Pop" <Da*****@cern.c h> wrote in message
news:c5******* ***@sunnews.cer n.ch...

In <Hw********@cwi .nl> "Dik T. Winter" <Di********@cwi .nl> writes:

>There has been an example of an executable which consisted only
>of bytes in the printable ASCII range.

ALL my Perl and /bin/sh executables consist only of bytes in the
printable ASCII range ;-)

It is arguable whether they qualify as "executable s".

Nothing to argue about it on a Unix system. If execve() can execute it,
it is an executable.

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Da*****@ifh.de