IPCS(1P) POSIX Programmer's Manual IPCS(1P)
PROLOG
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.
NAME
ipcs - report XSI interprocess communication facilities status
SYNOPSIS
ipcs [-qms][-a | -bcopt]
DESCRIPTION
The ipcs utility shall write information about active interprocess com-
munication facilities.
Without options, information shall be written in short format for mes-
sage queues, shared memory segments, and semaphore sets that are cur-
rently active in the system. Otherwise, the information that is dis-
played is controlled by the options specified.
OPTIONS
The ipcs facility supports the Base Definitions volume of
IEEE Std 1003.1-2001, 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 sem-
aphores.)
-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 seg-
ments.)
-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.)
OPERANDS
None.
STDIN
Not used.
INPUT FILES
* The group database
* The user database
ENVIRONMENT VARIABLES
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
IEEE Std 1003.1-2001, Section 8.2, Internationalization Vari-
ables 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.
ASYNCHRONOUS EVENTS
Default.
STDOUT
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 for-
mat:
"%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 spaces 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 col-
umn 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 corre-
sponding column to appear; "all" means that the column shall always
appear. Each column is separated by one or more <space>s. 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 writ-
ten 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 per-
mission to read, the second character indicates permission to write or
alter the facility entry, and the last character is a minus sign ( '-'
).
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; other-
wise, 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 mes-
sage 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 writ-
ten 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 writ-
ten 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 sema-
phore 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 .
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
Things can change while ipcs is running; the information it gives is
guaranteed to be accurate only when it was retrieved.
EXAMPLES
None.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
The System Interfaces volume of IEEE Std 1003.1-2001, msgrcv(),
msgsnd(), semget(), semop(), shmat(), shmdt(), shmget()
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 IPCS(1P)
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