umask question

[jc at trillian.mit.edu (John Chambers)]

David Kramer writes:
| On Fri, 12 Jul 2002, Nathan Meyers wrote:
| > The mode of a newly created file is set (and modified by the umask)
| > in the low-level creat(2) or open(2) system call. Most applications -
| > including anything using the C library's fopen(3) call - don't set the
| > execute bits at the time the file is created. So your umask setting
| > allows the execute bits to be set at file creation if the app requests
| > it... but the app still has to request it.
|
| Thanks.  That just seems so wrong to me though.  If I set a umask, why
| wouldn't creat() and open() honor it?  Isn't that what umask is for?

No; umask is for overriding the  permissions  requested  by
programs.   It's  a  way  of  saying  "I  don't  care  what
permissions a program requests;  the  following  permission
bits should be turned OFF."

There is an asymmetry here.  Logically, you could also have
a  second  mask that means "I don't care what permissions a
program requests; the following permission bits  should  be
turned  ON."  But  this has never existed, probably because
there hasn't been a groundswell of demand for  it.   People
are  usually  more concerned with blocking access than with
guaranteeing access.