coreutils: id invocation

1 
1 20.1 ‘id’: Print user identity
1 ==============================
1 
1 ‘id’ prints information about the given user, or the process running it
1 if no user is specified.  Synopsis:
1 
1      id [OPTION]... [USER]
1 
1    USER can be either a user ID or a name, with name look-up taking
11 precedence unless the ID is specified with a leading ‘+’.  ⇒
 Disambiguating names and IDs.
1 
1    By default, it prints the real user ID, real group ID, effective user
1 ID if different from the real user ID, effective group ID if different
1 from the real group ID, and supplemental group IDs.  In addition, if
1 SELinux is enabled and the ‘POSIXLY_CORRECT’ environment variable is not
1 set, then print ‘context=C’, where C is the security context.
1 
1    Each of these numeric values is preceded by an identifying string and
1 followed by the corresponding user or group name in parentheses.
1 
1    The options cause ‘id’ to print only part of the above information.
1 Also see ⇒Common options.
1 
1 ‘-g’
1 ‘--group’
1      Print only the group ID.
1 
1 ‘-G’
1 ‘--groups’
1      Print only the group ID and the supplementary groups.
1 
1 ‘-n’
1 ‘--name’
1      Print the user or group name instead of the ID number.  Requires
1      ‘-u’, ‘-g’, or ‘-G’.
1 
1 ‘-r’
1 ‘--real’
1      Print the real, instead of effective, user or group ID.  Requires
1      ‘-u’, ‘-g’, or ‘-G’.
1 
1 ‘-u’
1 ‘--user’
1      Print only the user ID.
1 
1 ‘-Z’
1 ‘--context’
1      Print only the security context of the process, which is generally
1      the user’s security context inherited from the parent process.  If
1      neither SELinux or SMACK is enabled then print a warning and set
1      the exit status to 1.
1 
1 ‘-z’
1 ‘--zero’
1      Delimit output items with NUL characters.  This option is not
1      permitted when using the default format.
1 
1      Example:
1           $ id -Gn --zero
1           users <NUL> devs <NUL>
1 
1    Primary and supplementary groups for a process are normally inherited
1 from its parent and are usually unchanged since login.  This means that
1 if you change the group database after logging in, ‘id’ will not reflect
1 your changes within your existing login session.  Running ‘id’ with a
1 user argument causes the user and group database to be consulted afresh,
1 and so will give a different result.
1 
1    An exit status of zero indicates success, and a nonzero value
1 indicates failure.
1