NAME

       id - return user identity

SYNOPSIS

       id [user]

       id -G[-n] [user]

       id -g[-nr] [user]

       id -u[-nr] [user]

DESCRIPTION

       If  no  user operand is provided, the id utility shall write the user and group IDs and the corresponding
       user and group names of the invoking process to standard output. If the effective and  real  IDs  do  not
       match,  both  shall  be  written.  If  multiple  groups  are  supported by the underlying system (see the
       description of {NGROUPS_MAX} in the System Interfaces volume of IEEE Std 1003.1-2001), the  supplementary
       group affiliations of the invoking process shall also be written.

       If  a  user operand is provided and the process has the appropriate privileges, the user and group IDs of
       the selected user shall be written. In this case, effective IDs shall be assumed to be identical to  real
       IDs.  If  the  selected  user  has more than one allowable group membership listed in the group database,
       these shall be written in the same  manner  as  the  supplementary  groups  described  in  the  preceding
       paragraph.

OPTIONS

       The  id  utility  shall  conform  to  the  Base Definitions volume of IEEE Std 1003.1-2001, Section 12.2,
       Utility Syntax Guidelines.

       The following options shall be supported:

       -G     Output all different group IDs (effective, real, and supplementary) only, using the format  "%u\n"
              .  If  there  is more than one distinct group affiliation, output each such affiliation, using the
              format " %u" , before the <newline> is output.

       -g     Output only the effective group ID, using the format "%u\n" .

       -n     Output the name in the format "%s" instead of the numeric ID using the format "%u" .

       -r     Output the real ID instead of the effective ID.

       -u     Output only the effective user ID, using the format "%u\n" .

OPERANDS

       The following operand shall be supported:

       user   The login name for which information is to be written.

STDIN

       Not used.

INPUT FILES

       None.

ENVIRONMENT VARIABLES

       The following environment variables shall affect the execution of id:

       LANG   Provide a default value for the internationalization variables that are unset or  null.  (See  the
              Base  Definitions  volume of IEEE Std 1003.1-2001, Section 8.2, Internationalization Variables for
              the  precedence  of  internationalization  variables  used  to  determine  the  values  of  locale
              categories.)

       LC_ALL If  set  to  a  non-empty  string value, override the values of all the other internationalization
              variables.

       LC_CTYPE
              Determine the locale for the interpretation of sequences of bytes of text data as characters  (for
              example, single-byte as opposed to multi-byte characters in arguments).

       LC_MESSAGES
              Determine  the locale that should be used to affect the format and contents of diagnostic messages
              written to standard error and informative messages written to standard output.

       NLSPATH
              Determine the location of message catalogs for the processing of LC_MESSAGES .

ASYNCHRONOUS EVENTS

       Default.

STDOUT

       The following formats shall be used when the LC_MESSAGES locale category specifies the POSIX  locale.  In
       other locales, the strings uid, gid, euid, egid, and groups may be replaced with more appropriate strings
       corresponding to the locale.

              "uid=%u(%s) gid=%u(%s)\n", <real user ID>, <user-name>,
                  <real group ID>, <group-name>

       If  the  effective and real user IDs do not match, the following shall be inserted immediately before the
       '\n' character in the previous format:

              " euid=%u(%s)"

       with the following arguments added at the end of the argument list:

              <effective user ID>, <effective user-name>

       If the effective and real group IDs do not match, the following shall be  inserted  directly  before  the
       '\n'  character  in  the format string (and after any addition resulting from the effective and real user
       IDs not matching):

              " egid=%u(%s)"

       with the following arguments added at the end of the argument list:

              <effective group-ID>, <effective group name>

       If the process has supplementary group affiliations or the selected user is allowed to belong to multiple
       groups, the first shall be added directly before the <newline> in the format string:

              " groups=%u(%s)"

       with the following arguments added at the end of the argument list:

              <supplementary group ID>, <supplementary group name>

       and the necessary number of the following added after that for any remaining supplementary group IDs:

              ",%u(%s)"

       and the necessary number of the following arguments added at the end of the argument list:

              <supplementary group ID>, <supplementary group name>

       If any of the user ID, group ID, effective user ID, effective group ID, or  supplementary/multiple  group
       IDs  cannot be mapped by the system into printable user or group names, the corresponding "(%s)" and name
       argument shall be omitted from the corresponding format string.

       When any of the options are specified, the output format shall be as described in the OPTIONS section.

STDERR

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES

       None.

EXTENDED DESCRIPTION

       None.

EXIT STATUS

       The following exit values shall be returned:

        0     Successful completion.

       >0     An error occurred.

CONSEQUENCES OF ERRORS

       Default.

       The following sections are informative.

APPLICATION USAGE

       Output produced by the -G option and by the default case could potentially produce  very  long  lines  on
       systems  that support large numbers of supplementary groups. (On systems with user and group IDs that are
       32-bit integers and with group names with a maximum of 8 bytes per name,  93  supplementary  groups  plus
       distinct effective and real group and user IDs could theoretically overflow the 2048-byte {LINE_MAX} text
       file  line limit on the default output case. It would take about 186 supplementary groups to overflow the
       2048-byte barrier using id -G). This is not expected to be a problem in practice, but in cases  where  it
       is a concern, applications should consider using fold -s before postprocessing the output of id.

EXAMPLES

       None.

RATIONALE

       The functionality provided by the 4 BSD groups utility can be simulated using:

              id -Gn [ user ]

       The  4  BSD  command  groups  was  considered,  but  it  was  not included because it did not provide the
       functionality of the id utility of the SVID. Also, it was thought that it would be easier to modify id to
       provide the additional functionality necessary to systems with multiple groups  than  to  invent  another
       command.

       The options -u, -g, -n, and -r were added to ease the use of id with shell commands substitution. Without
       these  options  it  is  necessary  to  use  some  preprocessor such as sed to select the desired piece of
       information. Since output such as that produced by:

              id -u -n

       is frequently wanted, it seemed desirable to add the options.

FUTURE DIRECTIONS

       None.

SEE ALSO

       fold , logname , who , the System  Interfaces  volume  of  IEEE Std 1003.1-2001,  getgid(),  getgroups(),
       getuid()

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition,
       Standard  for  Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers,
       Inc and The Open Group. In the event of any discrepancy between this version and the  original  IEEE  and
       The  Open  Group  Standard,  the  original  IEEE and The Open Group Standard is the referee document. The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group                                   2003                                                 ID(P)