Re: umask builtin

[Eduardo A . Bustamante López]

On Wed, Nov 08, 2017 at 12:04:08PM +0100, kalle wrote:
> in my version 4.4.0(1),
> `umask' gives me a numeric output of `0022',
> while `umask -S' gives me an output of `u=rwx,g=rx,o=rx'.
> Shouldn't umask -S also formulate the mask in a negative way, as does
> `umask'? Thus giving out `u=,g=w,o=w'?

Hm, is there a umask program that does this?

Looking at the shells I have installed, they all do pretty much the same:

dualbus@ubuntu:~$ for sh in bash dash ksh93 mksh posh zsh; do echo $sh $($sh -c 
'echo $(umask) $(umask -S)'); done
bash 0022 u=rwx,g=rx,o=rx
dash 0022 u=rwx,g=rx,o=rx
ksh93 0022 u=rwx,g=rx,o=rx
mksh 022 u=rwx,g=rx,o=rx
posh 022 u=rwx,g=rx,o=rx
zsh 022 u=rwx,g=rx,o=rx

Which is also what POSIX specifies: 
http://pubs.opengroup.org/onlinepubs/9699919799/utilities/umask.html

| If -S is specified, the message shall be in the following format:
| 
| "u=%s,g=%s,o=%s\n", <owner permissions>, <group permissions>,
|     <other permissions>
| 
| where the three values shall be combinations of letters from the set 
| { r, w, x}; the presence of a letter shall indicate that the corresponding
| bit is clear in the file mode creation mask.