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man pages section 8: System Administration Commands

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Updated: Thursday, June 13, 2019
 
 

id(8)

Name

id - return user identity

Synopsis

/usr/bin/id [-p] [user]
/usr/bin/id -a [-p] [user]
/usr/bin/id -G [-n] [user]
/usr/bin/id -g [-nr] [user]
/usr/bin/id -u [-nr] [user]
/usr/xpg4/bin/id [-p] [user]
/usr/xpg4/bin/id -a [-p] [user]
/usr/xpg4/bin/id -G [-n] [user]
/usr/xpg4/bin/id -g [-nr] [user]
/usr/xpg4/bin/id -u [-nr] [user]

Description

If no user operand is provided, the id utility writes 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 are written. If multiple groups are supported by the underlying system, /usr/xpg4/bin/id also writes the supplementary group affiliations of the invoking process.

If a user operand is provided and the process has the appropriate privileges, the user and group IDs of the selected user are written. In this case, effective IDs are assumed to be identical to real IDs. If the selected user has more than one allowable group membership listed in the group database, /usr/xpg4/bin/id writes them in the same manner as the supplementary groups described in the preceding paragraph.

Formats

The following formats are used when the LC_MESSAGES locale category specifies the "C" 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 are 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 is 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:

<effectivegroup-ID>, <effectivegroupname>

If the process has supplementary group affiliations or the selected user is allowed to belong to multiple groups, the first is added directly before the NEWLINE character 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 is omitted from the corresponding format string.

When any of the options are specified, the output format is as described under OPTIONS.

Options

The following options are supported by both /usr/bin/id and /usr/xpg4/bin/id. The –p and –a options are invalid if specified with any of the –G, –g, or –u options.

–p

Reports additionally the current project membership of the invoking process. The project is reported using the format:

"projid=%u(%s)"

which is inserted prior to the \n character of the default format described in the Formats section. The arguments

<project ID>,<project name>

are appended to the end of the argument list. If the project ID cannot be mapped by the system into a printable project name, the corresponding (%s) and name argument is omitted from the corresponding format string.

–a

Reports user name, user ID and all the groups to which the user belongs.

–G

Outputs 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 character is output.

–g

Outputs only the effective group ID, using the format "%u\n".

–n

Outputs the name in the format "%s" instead of the numeric ID using the format "%u".

–r

Outputs the real ID instead of the effective ID.

–u

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

Operands

The following operand is supported:

user

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

Environment Variables

See environ(7) for descriptions of the following environment variables that affect the execution of id: LANG, LC_ALL, LC_CTYPE, LC_MESSAGES, and NLSPATH.

Exit Status

The following exit values are returned:

0

Successful completion.

>0

An error occurred.

Attributes

See attributes(7) for descriptions of the following attributes:

/usr/bin/id

ATTRIBUTE TYPE
ATTRIBUTE VALUE
Availability
system/core-os, system/library/processor
Interface Stability
Committed

/usr/xpg4/bin/id

ATTRIBUTE TYPE
ATTRIBUTE VALUE
Availability
system/xopen/xcu4
Interface Stability
Standard

See Also

fold(1), logname(1), who(1), getgid(2), getgroups(2), getprojid(2), getuid(2), attributes(7), environ(7), standards(7)

Notes

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.