Originální popis anglicky:
id - return user identity
Návod, kniha: POSIX Programmer's Manual
id [user]
id -G
[-n]
[user]
id -g
[-nr]
[user]
id -u
[-nr]
[user]
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.
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" .
The following operand shall be supported:
- user
- The login name for which information is to be written.
Not used.
None.
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 .
Default.
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:
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):
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:
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:
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.
The standard error shall be used only for diagnostic messages.
None.
None.
The following exit values shall be returned:
- 0
- Successful completion.
- >0
- An error occurred.
Default.
The following sections are informative.
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.
None.
The functionality provided by the 4 BSD
groups utility can be simulated
using:
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:
is frequently wanted, it seemed desirable to add the options.
None.
fold ,
logname ,
who , the System Interfaces volume of
IEEE Std 1003.1-2001,
getgid(),
getgroups(),
getuid()
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
.
