|
HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|
|
PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
|
|
|
IPCS(1P) POSIX Programmer's Manual IPCS(1P)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
ipcs — report XSI interprocess communication facilities status
ipcs [-qms] [-a|-bcopt]
The ipcs utility shall write information about active interprocess
communication facilities.
Without options, information shall be written in short format for
message queues, shared memory segments, and semaphore sets that
are currently active in the system. Otherwise, the information
that is displayed is controlled by the options specified.
The ipcs utility shall conform to the Base Definitions volume of
POSIX.1‐2017, Section 12.2, Utility Syntax Guidelines.
The ipcs utility accepts the following options:
-q Write information about active message queues.
-m Write information about active shared memory segments.
-s Write information about active semaphore sets.
If -q, -m, or -s are specified, only information about those
facilities shall be written. If none of these three are specified,
information about all three shall be written subject to the
following options:
-a Use all print options. (This is a shorthand notation for
-b, -c, -o, -p, and -t.)
-b Write information on maximum allowable size. (Maximum
number of bytes in messages on queue for message queues,
size of segments for shared memory, and number of
semaphores in each set for semaphores.)
-c Write creator's user name and group name; see below.
-o Write information on outstanding usage. (Number of
messages on queue and total number of bytes in messages
on queue for message queues, and number of processes
attached to shared memory segments.)
-p Write process number information. (Process ID of the
last process to send a message and process ID of the
last process to receive a message on message queues,
process ID of the creating process, and process ID of
the last process to attach or detach on shared memory
segments.)
-t Write time information. (Time of the last control
operation that changed the access permissions for all
facilities, time of the last msgsnd() and msgrcv()
operations on message queues, time of the last shmat()
and shmdt() operations on shared memory, and time of the
last semop() operation on semaphores.)
None.
Not used.
* The group database
* The user database
The following environment variables shall affect the execution of
ipcs:
LANG Provide a default value for the internationalization
variables that are unset or null. (See the Base
Definitions volume of POSIX.1‐2017, 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.
NLSPATH Determine the location of message catalogs for the
processing of LC_MESSAGES.
TZ Determine the timezone for the date and time strings
written by ipcs. If TZ is unset or null, an unspecified
default timezone shall be used.
Default.
An introductory line shall be written with the format:
"IPC status from %s as of %s\n", <source>, <date>
where <source> indicates the source used to gather the statistics
and <date> is the information that would be produced by the date
command when invoked in the POSIX locale.
The ipcs utility then shall create up to three reports depending
upon the -q, -m, and -s options. The first report shall indicate
the status of message queues, the second report shall indicate the
status of shared memory segments, and the third report shall
indicate the status of semaphore sets.
If the corresponding facility is not installed or has not been
used since the last reboot, then the report shall be written out
in the format:
"%s facility not in system.\n", <facility>
where <facility> is Message Queue, Shared Memory, or Semaphore, as
appropriate. If the facility has been installed and has been used
since the last reboot, column headings separated by one or more
<space> characters and followed by a <newline> shall be written as
indicated below followed by the facility name written out using
the format:
"%s:\n", <facility>
where <facility> is Message Queues, Shared Memory, or Semaphores,
as appropriate. On the second and third reports the column
headings need not be written if the last column headings written
already provide column headings for all information in that
report.
The column headings provided in the first column below and the
meaning of the information in those columns shall be given in
order below; the letters in parentheses indicate the options that
shall cause the corresponding column to appear; ``all'' means that
the column shall always appear. Each column is separated by one or
more <space> characters. Note that these options only determine
what information is provided for each report; they do not
determine which reports are written.
T (all) Type of facility:
q Message queue.
m Shared memory segment.
s Semaphore.
This field is a single character written using the
format %c.
ID (all) The identifier for the facility entry. This field
shall be written using the format %d.
KEY (all) The key used as an argument to msgget(), semget(), or
shmget() to create the facility entry.
Note: The key of a shared memory segment is changed
to IPC_PRIVATE when the segment has been
removed until all processes attached to the
segment detach it.
This field shall be written using the format 0x%x.
MODE (all) The facility access modes and flags. The mode shall
consist of 11 characters that are interpreted as
follows.
The first character shall be:
S If a process is waiting on a msgsnd()
operation.
- If the above is not true.
The second character shall be:
R If a process is waiting on a msgrcv()
operation.
C or - If the associated shared memory segment is to
be cleared when the first attach operation is
executed.
- If none of the above is true.
The next nine characters shall be interpreted as three
sets of three bits each. The first set refers to the
owner's permissions; the next to permissions of others
in the usergroup of the facility entry; and the last
to all others. Within each set, the first character
indicates permission to read, the second character
indicates permission to write or alter the facility
entry, and the last character is a <hyphen-minus>
('-').
The permissions shall be indicated as follows:
r If read permission is granted.
w If write permission is granted.
a If alter permission is granted.
- If the indicated permission is not granted.
The first character following the permissions
specifies if there is an alternate or additional
access control method associated with the facility. If
there is no alternate or additional access control
method associated with the facility, a single <space>
shall be written; otherwise, another printable
character is written.
OWNER (all) The user name of the owner of the facility entry. If
the user name of the owner is found in the user
database, at least the first eight column positions of
the name shall be written using the format %s.
Otherwise, the user ID of the owner shall be written
using the format %d.
GROUP (all) The group name of the owner of the facility entry. If
the group name of the owner is found in the group
database, at least the first eight column positions of
the name shall be written using the format %s.
Otherwise, the group ID of the owner shall be written
using the format %d.
The following nine columns shall be only written out for message
queues:
CREATOR (a,c)
The user name of the creator of the facility entry. If
the user name of the creator is found in the user
database, at least the first eight column positions of
the name shall be written using the format %s.
Otherwise, the user ID of the creator shall be written
using the format %d.
CGROUP (a,c)
The group name of the creator of the facility entry.
If the group name of the creator is found in the group
database, at least the first eight column positions of
the name shall be written using the format %s.
Otherwise, the group ID of the creator shall be
written using the format %d.
CBYTES (a,o)
The number of bytes in messages currently outstanding
on the associated message queue. This field shall be
written using the format %d.
QNUM (a,o) The number of messages currently outstanding on the
associated message queue. This field shall be written
using the format %d.
QBYTES (a,b)
The maximum number of bytes allowed in messages
outstanding on the associated message queue. This
field shall be written using the format %d.
LSPID (a,p) The process ID of the last process to send a message
to the associated queue. This field shall be written
using the format:
"%d", <pid>
where <pid> is 0 if no message has been sent to the
corresponding message queue; otherwise, <pid> shall be
the process ID of the last process to send a message
to the queue.
LRPID (a,p) The process ID of the last process to receive a
message from the associated queue. This field shall be
written using the format:
"%d", <pid>
where <pid> is 0 if no message has been received from
the corresponding message queue; otherwise, <pid>
shall be the process ID of the last process to receive
a message from the queue.
STIME (a,t) The time the last message was sent to the associated
queue. If a message has been sent to the
corresponding message queue, the hour, minute, and
second of the last time a message was sent to the
queue shall be written using the format
%d:%2.2d:%2.2d. Otherwise, the format " no-entry"
shall be written.
RTIME (a,t) The time the last message was received from the
associated queue. If a message has been received from
the corresponding message queue, the hour, minute, and
second of the last time a message was received from
the queue shall be written using the format
%d:%2.2d:%2.2d. Otherwise, the format " no-entry"
shall be written.
The following eight columns shall be only written out for shared
memory segments.
CREATOR (a,c)
The user of the creator of the facility entry. If the
user name of the creator is found in the user
database, at least the first eight column positions of
the name shall be written using the format %s.
Otherwise, the user ID of the creator shall be written
using the format %d.
CGROUP (a,c)
The group name of the creator of the facility entry.
If the group name of the creator is found in the group
database, at least the first eight column positions of
the name shall be written using the format %s.
Otherwise, the group ID of the creator shall be
written using the format %d.
NATTCH (a,o)
The number of processes attached to the associated
shared memory segment. This field shall be written
using the format %d.
SEGSZ (a,b) The size of the associated shared memory segment. This
field shall be written using the format %d.
CPID (a,p) The process ID of the creator of the shared memory
entry. This field shall be written using the format
%d.
LPID (a,p) The process ID of the last process to attach or detach
the shared memory segment. This field shall be written
using the format:
"%d", <pid>
where <pid> is 0 if no process has attached the
corresponding shared memory segment; otherwise, <pid>
shall be the process ID of the last process to attach
or detach the segment.
ATIME (a,t) The time the last attach on the associated shared
memory segment was completed. If the corresponding
shared memory segment has ever been attached, the
hour, minute, and second of the last time the segment
was attached shall be written using the format
%d:%2.2d:%2.2d. Otherwise, the format " no-entry"
shall be written.
DTIME (a,t) The time the last detach on the associated shared
memory segment was completed. If the corresponding
shared memory segment has ever been detached, the
hour, minute, and second of the last time the segment
was detached shall be written using the format
%d:%2.2d:%2.2d. Otherwise, the format " no-entry"
shall be written.
The following four columns shall be only written out for semaphore
sets:
CREATOR (a,c)
The user of the creator of the facility entry. If the
user name of the creator is found in the user
database, at least the first eight column positions of
the name shall be written using the format %s.
Otherwise, the user ID of the creator shall be written
using the format %d.
CGROUP (a,c)
The group name of the creator of the facility entry.
If the group name of the creator is found in the group
database, at least the first eight column positions of
the name shall be written using the format %s.
Otherwise, the group ID of the creator shall be
written using the format %d.
NSEMS (a,b) The number of semaphores in the set associated with
the semaphore entry. This field shall be written using
the format %d.
OTIME (a,t) The time the last semaphore operation on the set
associated with the semaphore entry was completed. If
a semaphore operation has ever been performed on the
corresponding semaphore set, the hour, minute, and
second of the last semaphore operation on the
semaphore set shall be written using the format
%d:%2.2d:%2.2d. Otherwise, the format " no-entry"
shall be written.
The following column shall be written for all three reports when
it is requested:
CTIME (a,t) The time the associated entry was created or changed.
The hour, minute, and second of the time when the
associated entry was created shall be written using
the format %d:%2.2d:%2.2d.
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.
Things can change while ipcs is running; the information it gives
is guaranteed to be accurate only when it was retrieved.
None.
None.
None.
ipcrm(1p)
The Base Definitions volume of POSIX.1‐2017, Chapter 8,
Environment Variables, Section 12.2, Utility Syntax Guidelines
The System Interfaces volume of POSIX.1‐2017, msgrcv(3p),
msgsnd(3p), semget(3p), semop(3p), shmat(3p), shmdt(3p),
shmget(3p)
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 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 .
Any typographical or formatting errors that appear in this page
are most likely to have been introduced during the conversion of
the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2017 IPCS(1P)
Pages that refer to this page: ipcrm(1p)
|
HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|