POSIX shared memory for Linux network programming

Today we continue to study POSIX IPC objects, this time by learning how to use POSIX shared memory, starting with:

The following program is written to create a shared memory:

Compile run:

Where is POSIX's shared memory stored? The POSIX message queue of the upper secondary school is to create a message queue in the virtual file, which requires us to manually mount it to a directory to see, and the same,POSIX shared memory needs to be mounted , but this mount operation is done by the system , without our manual to operate, has been mounted to the/DEV/SHM under the following:

The next function to describe is to modify the size of the shared memory:

description: Actually the Ftruncate function can also modify the size of the file.

Modify the program below to use it:

Compile run:

where struct stat is structured as:

Modify the program as follows:

Compile run:

This is a relatively simple experiment:

Compile run:

Now that we have created a shared memory object, how do we use it? You need to use the following function:

To use the following, after the mapping succeeds, the data is written to memory and then read from memory:

Next, do a fault-tolerant processing:

In fact, the mapping failure has a special macro definition, which can be learned from the man help:

So, instead of the-1 program will be more readable:

Compile run:

What is this for? Or from the man help to find the answer:

So the cause of the problem is found, then modify the open mode to either:

Compile and run again:

There is no successful write, you need to write a read program to verify:

Compile run:

You can actually use the shell command to view the contents of the shared memory directly:

OK, this time to learn something relatively simple, next time to continue ~

POSIX shared memory for Linux network programming