Hi Valdis,

Thanks for your reply.

With your suggestions I have used the following code to test helloworld module and successfully saw "Hello World!' msg with dmesg command.

#include<linux/module.h>
#include<linux/init.h>
#include<linux/kernel.h>


MODULE_LICENSE("GPL");
MODULE_AUTHOR("Sankar");
MODULE_DESCRIPTION("Hello World Module");

static int __init helloworld_init(void)
{
    printk(KERN_INFO "Hello world!\n");
    return 0;
}

static void __exit helloworld_exit(void)
{
    printk(KERN_INFO "Cleaning up module.\n");
    return;
}

module_init(helloworld_init);
module_exit(helloworld_exit);

BR,

Sankar

On Sun, May 3, 2020 at 1:37 AM Valdis Klētnieks <valdis.kletnieks@vt.edu> wrote:

On Sat, 02 May 2020 23:46:08 +0530, Majji SankaraRao said:

> I want to practice writing modules in Linux version 5.3.0-51-generic.
> So please guide me by providing related documentation/Steps.

Create two functions, one for initializing your module, and one for cleaning up at exit.

static int __init init_my_module(void)
{
        printk(KERN_DEBUG "Hello World!\n");
}

static void __exit exit_my_module(void)
{
        printk(KERN_DEBUG "Say goodnight, Gracie\n");
}
module_init(init_my_module);
module_exit(exit_my_module);

Everything else isn't how to write a module, it's about how to write whatever
code is needed for the function you're trying to add, whether it's a file
system, or a new netfilter target, or a device driver, or a network congestion
control module, or whatever...

And that code basically doesn't care if it's a module or if it's built in to
the kernel.

So the question becomes:  What did you want to do inside the kernel?