Ubuntu Manpage: ipcs - report XSI interprocess communication facilities status

NAME

       ipcs - report XSI interprocess communication facilities status

SYNOPSIS

       ipcs [-qms][-a | -bcopt]

DESCRIPTION

       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.

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 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.)

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 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.

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 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 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 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>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 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 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; 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 .

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:

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 .

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.

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 .

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