l i n u x - u s e r s - g r o u p - o f - d a v i s
Next Meeting:
July 7: Social gathering
Next Installfest:
Latest News:
Jun. 14: June LUGOD meeting cancelled
Page last updated:
2002 Jun 13 16:41

The following is an archive of a post made to our 'vox mailing list' by one of its subscribers.

Report this post as spam:

(Enter your email address)
Re: [vox] cat and >> - how does it know?
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [vox] cat and >> - how does it know?

File locking?


On Thu, 13 Jun 2002, nbs wrote:

> Not paying attention to tab-completion, I just accidentally did this:
>   cat somefile >> somefile
> Luckily, "cat" noticed, and complained:
>   cat: somefile: input file is output file
> But - how does it know?  Using just argv/argc, all "cat" would know
> is that you want to throw "somefile" to stdout.
> The shell is the one worrying about the ">>" and everything after it.
> I'm guessing the shell makes a note of what it's doing (redirecting/appending)
> and makes that info. available to the process (in this case, cat),
> who can notice and, in this case, complain.
> How, exactly, does it do this?
> -bill!
> (too lazy to dig up source to /bin/cat ;) )
> PS - This was under both tcsh and bash
> _______________________________________________
> vox mailing list
> vox@lists.lugod.org
> http://lists.lugod.org/mailman/listinfo/vox

Mark K. Kim
PGP key available upon request.

vox mailing list

LUGOD Group on LinkedIn
Sign up for LUGOD event announcements
Your email address:
LUGOD Group on Facebook
'Like' LUGOD on Facebook:

Hosting provided by:
Sunset Systems
Sunset Systems offers preconfigured Linux systems, remote system administration and custom software development.

LUGOD: Linux Users' Group of Davis
PO Box 2082, Davis, CA 95617
Contact Us

LUGOD is a 501(c)7 non-profit organization
based in Davis, California
and serving the Sacramento area.
"Linux" is a trademark of Linus Torvalds.

Sponsored in part by:
Sunset Systems
Who graciously hosts our website & mailing lists!