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Mdoc cleanup.
This commit is contained in:
parent
95522ed527
commit
9de8ddb8bc
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=24093
@ -46,15 +46,18 @@
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returns the message queue identifier associated with
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.Fa key .
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A message queue identifier is a unique integer greater than zero.
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.Pp
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A message queue is created if either
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.Fa key
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is equal to IPC_PRIVATE, or
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is equal to
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.Dv IPC_PRIVATE ,
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or
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.Fa key
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does not have a message queue identifier associated with it, and the IPC_CREAT
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does not have a message queue identifier associated with it, and the
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.Dv IPC_CREAT
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bit is set in
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.Fa msgflg.
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.Pp
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If a new message queue is created, the data structure associated with it (the
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.Va msqid_ds
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structure, see
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@ -83,11 +86,11 @@ is set to the lower 9 bits of
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.Va msg_rtime ,
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and
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.Va msg_stime
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are set to 0
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are set to 0.
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.It
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.Va msg_qbytes
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is set to the system wide maximum value for the number of bytes in a queue
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(MSGMNB).
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.Pf ( Dv MSGMNB ) .
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.It
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.Va msg_ctime
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is set to the current time.
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@ -104,7 +107,11 @@ A message queue is already associated with
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.Fa key
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and the caller has no permission to access it.
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.It Bq Er EEXIST
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Both IPC_CREAT and IPC_EXCL are set in
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Both
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.Dv IPC_CREAT
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and
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.Dv IPC_EXCL
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are set in
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.Fa msgflg ,
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and a message queue is already associated with
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.Fa key .
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@ -112,7 +119,8 @@ and a message queue is already associated with
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A new message queue could not be created because the system limit for
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the number of message queues has been reached.
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.It Bq Er ENOENT
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IPC_CREAT was not set in
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.Dv IPC_CREAT
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was not set in
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.Fa msgflg
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and no message queue associated with
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.Fa key
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@ -53,12 +53,13 @@ This structure should consist of the following members:
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long mtype; /* message type */
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char mtext[1]; /* body of message */
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.Ed
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.Pp
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.Va mtype
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is an integer greater than 0 that can be used for selecting messages,
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.Va mtext
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is an array of bytes, with a size up to that of the system limit (MSGMAX).
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is an array of bytes, with a size up to that of the system limit
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.Pf ( Dv MSGMAX ) .
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.Pp
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The value of
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.Fa msgtyp
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has one of the following meanings:
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@ -78,26 +79,36 @@ less than or equal to the absolute value of
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.Fa msgtyp
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will be received.
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.El
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.Pp
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.Fa msgsz
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specifies the maximum length of the requested message. If the received
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message has a length greater than
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.Fa msgsz
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it will be silently truncated if the MSG_NOERROR flag is set in
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it will be silently truncated if the
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.Dv MSG_NOERROR
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flag is set in
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.Fa msgflg ,
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otherwise an error will be returned.
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.Pp
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If no matching message is present on the message queue specified by
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.Fa msqid ,
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the behavior of
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.Fn msgrcv
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depends on whether the IPC_NOWAIT flag is set in
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depends on whether the
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.Dv IPC_NOWAIT
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flag is set in
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.Fa msgflg
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or not. If IPC_NOWAIT is set,
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or not. If
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.Dv IPC_NOWAIT
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is set,
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.Fn msgrcv
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will immediately return a value of -1, and set
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.Va errno
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to EAGAIN. If IPC_NOWAIT is not set, the calling process will be blocked
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to
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.Er EAGAIN .
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If
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.Dv IPC_NOWAIT
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is not set, the calling process will be blocked
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until:
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.Bl -bullet
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.It
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@ -105,13 +116,15 @@ A message of the requested type becomes available on the message queue.
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.It
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The message queue is removed, in which case -1 will be returned, and
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.Va errno
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set to EINVAL.
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set to
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.Er EINVAL .
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.It
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A signal is received and caught. -1 is returned, and
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.Va errno
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set to EINTR.
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set to
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.Er EINTR .
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.El
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.Pp
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If a message is successfully received, the data structure associated with
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.Fa msqid
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is updated as follows:
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@ -144,18 +157,20 @@ will fail if:
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.Bl -tag -width Er
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.It Bq Er EINVAL
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.Fa msqid
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is not a valid message queue identifier
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is not a valid message queue identifier.
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.Pp
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The message queue was removed while
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.Fn msgrcv
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was waiting for a message of the requested type to become available on it.
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.Pp
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.Fa msgsz
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is less than 0.
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.It Bq Er E2BIG
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A matching message was received, but its size was greater than
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.Fa msgsz
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and the MSG_NOERROR flag was not set in
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and the
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.Dv MSG_NOERROR
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flag was not set in
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.Fa msgflg .
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.It Bq Er EACCESS
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The calling process does not have read access to the message queue.
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@ -166,16 +181,27 @@ points to an invalid address.
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The system call was interrupted by the delivery of a signal.
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.It Bq Er EAGAIN
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There is no message of the requested type available on the message queue,
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and IPC_NOWAIT is set in
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and
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.Dv IPC_NOWAIT
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is set in
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.Fa msgflg .
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.Sh SEE ALSO
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.Xr msgctl 3 ,
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.Xr msgget 3 ,
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.Xr msgsnd 3
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.Sh BUGS
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NetBSD and FreeBSD do not define the EIDRM error value, which should be used in
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the case of a removed message queue, nor the ENOMSG value, which
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should be used when no suitable message is available and IPC_NOWAIT
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.Tn NetBSD
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and
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.Tn FreeBSD
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do not define the
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.Er EIDRM
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error value, which should be used in
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the case of a removed message queue, nor the
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.Er ENOMSG
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value, which
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should be used when no suitable message is available and
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.Dv IPC_NOWAIT
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is set.
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.Sh HISTORY
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Message queues appeared in the first release of AT&T Unix System V.
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Message queues appeared in the first release of
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AT&T Unix System V.
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@ -53,17 +53,18 @@ consist of the following members:
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long mtype; /* message type */
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char mtext[1]; /* body of message */
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.Ed
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.Pp
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.Va mtype
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is an integer greater than 0 that can be used for selecting messages (see
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.Xr msgrcv 3 ) ,
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.Va mtext
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is an array of bytes, with a size up to that of the system limit (MSGMAX).
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is an array of bytes, with a size up to that of the system limit
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.Pf ( Dv MSGMAX ) .
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.Pp
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If the number of bytes already on the message queue plus
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.Fa msgsz
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is bigger than the maximum number of bytes on the message queue (
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.Va msg_qbytes ,
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is bigger than the maximum number of bytes on the message queue
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.Pf ( Va msg_qbytes ,
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see
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.Xr msgctl 3 ) ,
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or the number of messages on all queues system-wide is already equal to
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@ -73,9 +74,13 @@ determines the action of
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.Fn msgsnd .
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If
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.Fa msgflg
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has IPC_NOWAIT mask set in it, the call will return immediately. If
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has
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.Dv IPC_NOWAIT
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mask set in it, the call will return immediately. If
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.Fa msgflg
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does not have IPC_NOWAIT set in it, the call will block until:
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does not have
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.Dv IPC_NOWAIT
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set in it, the call will block until:
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.Bl -bullet
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.It
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The condition which caused the call to block does no longer exist.
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@ -83,13 +88,15 @@ The message will be sent.
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.It
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The message queue is removed, in which case -1 will be returned, and
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.Va errno
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is set to EINVAL.
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is set to
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.Er EINVAL .
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.It
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The caller catches a signal. The call returns with
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.Va errno
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set to EINTR.
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set to
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.Er EINTR .
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.El
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.Pp
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After a successful call, the data structure associated with the message
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queue is updated in the following way:
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.Bl -bullet
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@ -117,12 +124,12 @@ will fail if:
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.It Bq Er EINVAL
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.Fa msqid
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is not a valid message queue identifier
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.Pp
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The message queue was removed while
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.Fn msgsnd
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was waiting for a resource to become available in order to deliver the
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message.
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.Pp
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.Fa msgsz
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is less than 0, or greater than
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.Va msg_qbytes .
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@ -130,7 +137,9 @@ is less than 0, or greater than
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The calling process does not have write access to the message queue.
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.It Bq Er EAGAIN
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There was no space for this message either on the queue, or in the whole
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system, and IPC_NOWAIT was set in
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system, and
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.Dv IPC_NOWAIT
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was set in
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.Fa msgflg .
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.It Bq Er EFAULT
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.Fa msgp
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@ -139,7 +148,12 @@ points to an invalid address.
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The system call was interrupted by the delivery of a signal.
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.El
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.Sh BUGS
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NetBSD and FreeBSD do not define the EIDRM error value, which should be used
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.Tn NetBSD
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and
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.Tn FreeBSD
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do not define the
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.Er EIDRM
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error value, which should be used
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in the case of a removed message queue.
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.Sh HISTORY
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Message queues appeared in the first release of AT&T Unix System V.
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