diff options
Diffstat (limited to 'man7/mq_overview.7')
| -rw-r--r-- | man7/mq_overview.7 | 30 |
1 files changed, 15 insertions, 15 deletions
diff --git a/man7/mq_overview.7 b/man7/mq_overview.7 index b022ea0..223f238 100644 --- a/man7/mq_overview.7 +++ b/man7/mq_overview.7 @@ -3,7 +3,7 @@ .\" .\" SPDX-License-Identifier: Linux-man-pages-copyleft .\" -.TH mq_overview 7 2023-02-05 "Linux man-pages 6.05.01" +.TH mq_overview 7 2023-10-31 "Linux man-pages 6.7" .SH NAME mq_overview \- overview of POSIX message queues .SH DESCRIPTION @@ -14,7 +14,7 @@ This API is distinct from that provided by System V message queues .BR msgsnd (2), .BR msgrcv (2), etc.), but provides similar functionality. -.PP +.P Message queues are created and opened using .BR mq_open (3); this function returns a @@ -29,7 +29,7 @@ that is, a null-terminated string of up to followed by one or more characters, none of which are slashes. Two processes can operate on the same queue by passing the same name to .BR mq_open (3). -.PP +.P Messages are transferred to and from a queue using .BR mq_send (3) and @@ -45,7 +45,7 @@ and A process can request asynchronous notification of the arrival of a message on a previously empty queue using .BR mq_notify (3). -.PP +.P A message queue descriptor is a reference to an .I "open message queue description" (see @@ -58,7 +58,7 @@ as the corresponding message queue descriptors in the parent. Corresponding message queue descriptors in the two processes share the flags .RI ( mq_flags ) that are associated with the open message queue description. -.PP +.P Each message has an associated .IR priority , and messages are always delivered to the receiving process @@ -71,7 +71,7 @@ On Linux, returns 32768, but POSIX.1 requires only that an implementation support at least priorities in the range 0 to 31; some implementations provide only this range. -.PP +.P The remainder of this section describes some specific details of the Linux implementation of POSIX message queues. .SS Library interfaces and system calls @@ -265,33 +265,33 @@ On Linux, message queues are created in a virtual filesystem. but the details are likely to differ.) This filesystem can be mounted (by the superuser) using the following commands: -.PP +.P .in +4n .EX .RB "#" " mkdir /dev/mqueue" .RB "#" " mount \-t mqueue none /dev/mqueue" .EE .in -.PP +.P The sticky bit is automatically enabled on the mount directory. -.PP +.P After the filesystem has been mounted, the message queues on the system can be viewed and manipulated using the commands usually used for files (e.g., .BR ls (1) and .BR rm (1)). -.PP +.P The contents of each file in the directory consist of a single line containing information about the queue: -.PP +.P .in +4n .EX .RB "$" " cat /dev/mqueue/mymq" QSIZE:129 NOTIFY:2 SIGNO:0 NOTIFY_PID:8260 .EE .in -.PP +.P These fields are as follows: .TP .B QSIZE @@ -325,7 +325,7 @@ This means that a message queue descriptor can be monitored using or .BR epoll (7). This is not portable. -.PP +.P The close-on-exec flag (see .BR open (2)) is automatically set on the file descriptor returned by @@ -344,7 +344,7 @@ POSIX message queues provide a better designed interface than System V message queues; on the other hand POSIX message queues are less widely available (especially on older systems) than System V message queues. -.PP +.P Linux does not currently (Linux 2.6.26) support the use of access control lists (ACLs) for POSIX message queues. .SH BUGS @@ -356,7 +356,7 @@ limit could be raised, and the ceiling was enforced even for privileged processes. This ceiling value was removed in Linux 3.14, and patches to stable Linux 3.5.x to Linux 3.13.x also removed the ceiling. -.PP +.P As originally implemented (and documented), the QSIZE field displayed the total number of (user-supplied) bytes in all messages in the message queue. |