Re: Supplemental groups count in Linux

On Sun, 8 Dec 2024 19:23:50 -0500, DFS <guhnoo-basher@linux.advocaca>
wrote in <vj5daf$30up$2@dont-email.me>:

On 12/8/2024 12:12 AM, vallor wrote:

NGROUPS_MAX is the maximum supplemental group count for a Unix login.
 
On Linux, it is 65536.
 
But on MacOS and NetBSD, it is 16 -- which is the old standard.
 
Even worse, MacOS has all but filled the supplemental groups with
gid's for its own housekeeping:
 
$ for II in `id -G -n`; do echo $II ; done
staff
everyone
localaccounts
_appserverusr
admin
_appserveradm
_lpadmin
_appstore
_lpoperator
_developer
_analyticsusers
com.apple.access_ftp
com.apple.access_screensharing
com.apple.access_ssh
com.apple.access_remote_ae
 
$ for II in `id -G -n`; do echo $II ; done | wc -l
       15
 
What a waste of space!  On Linux:
 
$ for II in `id -G -n`; do echo $II ; done
scott
adm
cdrom
sudo
dip
plugdev
lpadmin
sambashare
wireshark
libvirt
nordvpn
 
$ for II in `id -G -n`; do echo $II ; done | wc -l
11
 
Conclusion:  Linux is a modern OS, with much more administrative
flexibility.  Complex user-sharing configurations can be set
up -- encompassing, if needed, thousands of supplemental
groups.
 
p.s. If someone could run this on Windows and report the value,
I'd much appreciate it:
 
  - - %<- cut here - %<- - -
#include <stdio.h>
#include <limits.h>
 
int main (void)
{
 
printf("%d\n",NGROUPS_MAX);
 
return 0;
}
 
  - - %<- cut here - %<- - -

 
 
D:\temp>tcc ngroups.c -o ngroups.exe
ngroups.c:6: error: 'NGROUPS_MAX' undeclared

No POSIX for you.

Seriously, though, try this:

#define _POSIX_
#include <stdio.h>
#include <limits.h>

int main (void)
{

printf("%d\n",NGROUPS_MAX);

return 0;
}

I know the answer though, because I downloaded tcc and looked
in limits.h -- which you could have done.  (But I don't think
the value in there properly reflects the system value -- couldn't
find a prototype for getgroups(3).)

--
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   "Windows: just another pane in the glass."