id —
return user identity
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
displayed.
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:
-c- Display the login class of the real user ID or the specified
user.
-G- Display the different group IDs (effective, real and supplementary) as
whitespace 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 displayed as a
name, preceded by the keyword “rgid”. The list of groups to
which the user belongs is then displayed as names, preceded by the keyword
“groups”. If there is a login class specified for the user
in the passwd(5) database, it is
displayed, preceded by the keyword “class”. Each display is
on a separate line.
-R- Display the routing table of the current process.
-r- Display the real ID for the
-g and
-u options instead of the effective ID.
-u- Display the effective user ID as a number.
The id utility exits 0 on success,
and >0 if an error occurs.
The id utility is compliant with the
IEEE Std 1003.1-2008 (“POSIX.1”)
specification.
The flags [-cpR] are extensions to that
specification.
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.