ID(1) BSD Reference Manual ID(1)
id - return user identity
id -G [-n] [user]
id -g [-nr] [user]
id -u [-nr] [user]
The id utility displays the user and group names and numeric IDs, of the
calling process, to the standard output. If the real and effective IDs
are different, both are displayed, otherwise only the real ID is dis-
If a user (login name or user ID) is specified, the user and group IDs of
that user are displayed. In this case, the real and effective IDs are
assumed to be the same.
The options are as follows:
-G Display the different group IDs (effective, real and supplemen-
tary) as white-space separated numbers, in no particular order.
-g Display the effective group ID as a number.
-n Display the name of the user or group ID for the -G, -g and -u
options instead of the number. If any of the ID numbers cannot
be mapped into names, the number will be displayed as usual.
-p Make the output human-readable. If the user name returned by
getlogin(2) is different from the login name referenced by the
user ID, the name returned by getlogin(2) is displayed, preceded
by the keyword ``login''. The user ID as a name is displayed,
preceded by the keyword ``uid''. If the effective user ID is
different from the real user ID, the real user ID is displayed as
a name, preceded by the keyword ``euid''. If the effective group
ID is different from the real group ID, the real group ID is dis-
played as a name, preceded by the keyword ``rgid''. The list of
groups to which the user belongs is then displayed as names, pre-
ceded by the keyword ``groups''. Each display is on a separate
-r Display the real ID for the -g and -u options instead of the ef-
-u Display the effective user ID as a number.
The id utility exits 0 on success, and >0 if an error occurs.
The id function is expected to conform to IEEE Std1003.2 (``POSIX'').
The historic groups(1) command is equivalent to ``id -Gn [user]''.
The historic whoami(1) command is equivalent to ``id -un''.
The id command first appeared in 4.4BSD.