/usr/bin/id

Usage: /usr/bin/id [OPTION]... [USER]...
Print user and group information for each specified USER,
or (when USER omitted) for the current process.

  -a
         ignore, for compatibility with other versions
  -Z, --context
         print only the security context of the process
  -g, --group
         print only the effective group ID
  -G, --groups
         print all group IDs
  -n, --name
         print a name instead of a number, for -u, -g, -G
  -r, --real
         print the real ID instead of the effective ID, with -u, -g, -G
  -u, --user
         print only the effective user ID
  -z, --zero
         delimit entries with NUL characters, not whitespace;
         not permitted in default format
      --help
         display this help and exit
      --version
         output version information and exit

Without any OPTION, print some useful set of identified information.

Report bugs to: <bug-coreutils@gnu.org>.
GNU coreutils home page: <https://www.gnu.org/software/coreutils/>
General help using GNU software: <https://www.gnu.org/gethelp/>
Full documentation <https://www.gnu.org/software/coreutils/id>
or available locally via: info '(coreutils) id invocation'