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From: mouse@mcgill-vision.UUCP (der Mouse)
Newsgroups: net.unix-wizards
Subject: /tmp versus temporary file types
Message-ID: <136@mcgill-vision.UUCP>
Date: Tue, 3-Sep-85 03:51:13 EDT
Article-I.D.: mcgill-v.136
Posted: Tue Sep  3 03:51:13 1985
Date-Received: Sat, 7-Sep-85 05:52:49 EDT
Organization: McGill University, Montreal
Lines: 35

[paraphrasing]
> ....like to see some discussion on: /tmp.
> ....anybody can 'rm /tmp/*', read files there, etc....

Anyone can rm /tmp/*, true.  Read on.
Anyone can read files there only if the program which creates them gives
them  a mode which allows  read  access.   Usually if you umask  007  or
anything ending in a 7 then world cannot access to files you create.

     When I write something which wants a temporary  file I do something
like this:

	/* generate temporary filename via mktemp() or some such */
	/* temporary filename in tmpfn */
	unlink(tempfn); /* in case a file by that name already exists */
	fd = open(tempfn,O_CREAT|O_TRUNC|O_RDWR,0644);
	/* O_RDWR and 0644 are variable depending on the application */
	unlink(tempfn);
	/* now the temporary file sticks around on disk as long as I have */
	/* it open, but is COMPLETELY inaccessible except to this process */
	/* and any children I fork */

     Granted, this does not work  when  you want another program to read
the file by name.    Just another reason to  make  everything work as  a
filter  (:-).  This sort of code has proven useful  in several  programs
which  merely want someplace  to  put huge (>  max  malloc()able  space)
amounts of temporary data.
-- 
					der Mouse

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