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From: jv@mhres.mh.nl (Johan Vromans)
Newsgroups: comp.unix.wizards
Subject: Using argv to show process status
Message-ID: <1217@mhres.mh.nl>
Date: Thu, 20-Aug-87 04:41:26 EDT
Article-I.D.: mhres.1217
Posted: Thu Aug 20 04:41:26 1987
Date-Received: Sat, 22-Aug-87 09:44:55 EDT
Organization: Multihouse NV, the Netherlands
Lines: 31
Keywords: argv ps

Some UN*X implementations allow a process to change its argv, which
subsequently shows up when doing a "ps". This can be used to reveal a
process' continuation status and such.

I have found out, that the process should execute something like

	strcpy (argv[0], "Hi there, I'm doing fine.");

changing argv with  

	argv[0] = "Hello, world!";

does not work.

My questions:

 - How does this work? Does it work only on BSD type systems, any others?

 - Whose memory is the process writing into? What happens if the process
   writes more bytes than the caller specified in the command line?

 - How can the remainder of the command line be blanked. Filling with a few
   null-characters seems not to be sufficient.


Thanks in advance.

-- 
Johan Vromans                           | jv@mh.nl via European backbone
Multihouse N.V., Gouda, the Netherlands | uucp: ..{seismo!}mcvax!mh.nl!jv
"It is better to light a candle than to curse the darkness"