What is the use of msgctl()?

What is the use of msgctl()?

The msgctl() function allows the caller to control the message queue specified by the msqid parameter. Remove the message queue identifier msqid from the system and destroy any messages on the message queue.

What is IPC_RMID?

IPC_RMID. Remove the message queue identifier specified by msqid from the system and destroy the message queue and msqid_ds data structure associated with it. IPC_RMD can only be executed by a process with appropriate privileges or one that has an effective user ID equal to the value of msg_perm.

How do you delete a message queue?

You can remove a message queue using the ipcrm command (see the ipcrm(1) reference page), or by calling msgctl() and passing the IPC_RMID command code. In many cases, a message queue is meant for use within the scope of one program only, and you do not want the queue to persist after the termination of that program.

Which command is used to know the status of a message queue in IPC* 1 point IPC_ stat IPC_ set IPC stat IPC set?

The cmd argument is one of: IPC_STAT. — Place information about the status of the queue in the data structure pointed to by buf. The process must have read permission for this call to succeed.

What is the return value of Msgget () system call?

On success, msgget() returns the message queue identifier (a nonnegative integer). On failure, -1 is returned, and errno is set to indicate the error.

What is the key in Shmget?

The key argument is an integral value which identifies the shared memory segment desired. A key value of IPC_PRIVATE requests a new shared memory segment without an associated key, and which can be accessed only by the segment id returned by shmget . The size argument specifies the required size of the segment.

What is FTOK?

DESCRIPTION. The ftok() function returns a key based on path and id. The function returns the same key for all paths that point to the same file when called with the same id value. If ftok() is called with different id values or path points to different files on the same file system, it returns different keys.

How does pipe differ from queue?

In a message queue, a writer process can write a message and exit. A reader process can read a message later. A pipe is deleted from the system if there is no linked receiver/sender process is present. A message queue remains active in the system until explicitly deleted by some process.

What is Posix message queue?

POSIX message queues allow processes to exchange data in the form of messages. Each message queue is identified by a name of the form /somename; that is, a null-terminated string of up to NAME_MAX (i.e., 255) characters consisting of an initial slash, followed by one or more characters, none of which are slashes.

Which is the fastest form of IPC?

Shared memory
Shared memory is the fastest form of interprocess communication. The main advantage of shared memory is that the copying of message data is eliminated.

How do I create a message queue?

1. Open Control Panel->Administrative Tools->Computer Management.
2. Open Services and Applications->Message Queueing.
3. To add a queue, select New->Private Queue from the right-click menu.
4. A New Queue dialog box will appear.
5. Check the Transactional box if needed.
6. Then click OK.