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How to add /proc file system entry for the module, illustrated here

here is simple example to demonstrate adding /proc file system entry for the module, as follows


shiv@ubuntu:~/ds/linx$ cat heloproc.c
/*
 * Kernel program demo to illustrate how to create/add entry to
 * /proc file system
 */
#include <linux/init.h>
#include <linux/module.h>
#include <linux/proc_fs.h>

/* Module license */
MODULE_LICENSE("Dual BSD/GPL");

/*
 * This is the service routine for added /proc entry
 * when user try to look into /proc/<entry added> this routine will be executed
 *
 * char *buf - below is page allocated by kernel and passed to service routine
 * eof and start would be used only when using /proc for
 * getting more than one page (usually page is 4KB)
 * for complete info you could refer linux docs
 */

int demo_read_fs(char *buf, char **start, off_t offset, int count, int *eof, void *data)
{
  int len=0;

 len = sprintf(buf, "This is Demo proc fs creation\n\n");

 return len;

}

/*
 * create_proc_read_entry() used for adding /proc fs entry in linux
 * name of the entry will be "Demoprocfs"
 * and it will be seen as /proc/Demoprocfs
 */

static void add_proc_fs_entry()
{
  create_proc_read_entry("Demoprocfs", 0, NULL, demo_read_fs, NULL);
}

/* module init */

static int proc_fs_init(void)
{
   printk(KERN_ALERT "loading demo proc fs file module\n");
   /* add /proc fs entry */
   add_proc_fs_entry(); 
   return 0;
}

/* module unloaded when we remove it */
static void proc_fs_exit(void)
{
    printk(KERN_ALERT "unloaded demo proc fs file module");
    /*
     * when we unload module, it will remove /proc entry added
     * when loading the module
     */
    remove_proc_entry("Demoprocfs", NULL);
}

module_init(proc_fs_init);
module_exit(proc_fs_exit);


/* end of the program */

Testing of sample code written above




reference:
Linux device drivers by Jonathan Corbert, Alessandro, Greg Kroah-Hartman, Oreilly publication
Linux source : http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=tree;hb=HEAD


Thanks,
-Shiv

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