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(Linux kernel module)
| Date: | 08/02/05 |
| Author: | Stefan Scheler |
| URL: | http://sts.synflood.de/ |
| Comments: | 15 |
| Info: | http://www.tldp.org/LDP/khg/HyperNews/get/khg.html |
| Score: |  (3.02 in 325 votes) |
/* The 99 Bottles of Beer Linux Kernel Module v1.1
* (supports multiple driver instances)
*
* by Stefan Scheler <sts[at]synflood[dot]de>
* August 2nd, 2005 - Ernstthal, Germany
*
* Usage:
* 1) compile the module
* 2) create the device: mknod /dev/bottles c 240 0
* 3) load the module: insmod bottles.ko
* 4) print the song with: cat /dev/bottles
*/
#include <linux/fs.h>
#include <linux/version.h>
#include <linux/module.h>
#include <linux/init.h>
#include <asm/uaccess.h>
#define DRIVER_MAJOR 240
#define BUFFERSIZE 160
#define PLURALS(b) (b>1)?"s":""
MODULE_AUTHOR("Stefan Scheler <sts[at]synflood[dot]de>");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("The 99 Bottles of Beer Linux Kernel Module");
MODULE_SUPPORTED_DEVICE("Bottle of Beer");
struct _instance_data {
int bytes_avail, bytes_sent, bottles;
char buf[BUFFERSIZE];
};
static void fill_buffer(char *buf, int b) {
char line[BUFFERSIZE/2];
if (b>0) {
sprintf(buf, "%d bottle%s of beer on the wall, %d bottle%s of beer.\n" \
"Take one down and pass it around, ", b, PLURALS(b), b, PLURALS(b));
if (b==1)
strcat(buf, "no more bottles of beer on the wall.\n");
else {
sprintf(line, "%d bottle%s of beer on the wall.\n", b-1, PLURALS(b-1));
strcat(buf, line);
}
} else {
sprintf(buf, "No more bottles of beer on the wall, no more bottles of beer.\n" \
"Go to the store and buy some more, 99 bottles of beer on the wall.\n");
}
}
static ssize_t driver_read(struct file *instance, char *userbuffer, size_t count, loff_t *offset) {
struct _instance_data *iptr = (struct _instance_data *)instance->private_data;
int to_copy;
int not_copied;
refillbuffer:
fill_buffer(iptr->buf, iptr->bottles);
iptr->bytes_avail = strlen(iptr->buf)+1;
to_copy = iptr->bytes_avail-iptr->bytes_sent;
if (to_copy>0) {
if (to_copy> count) to_copy=count;
not_copied=copy_to_user(userbuffer, iptr->buf+iptr->bytes_sent, to_copy);
iptr->bytes_sent += to_copy-not_copied;
return (to_copy-not_copied);
}
if ((to_copy==0) && (iptr->bottles>0)) {
iptr->bytes_sent=0;
iptr->bottles--;
goto refillbuffer;
}
return 0;
}
int driver_open(struct inode *devicefile, struct file *instance) {
struct _instance_data *iptr;
iptr = (struct _instance_data *)kmalloc(sizeof(struct _instance_data), GFP_KERNEL);
if (!iptr)
return -1;
iptr->bytes_sent = 0;
iptr->bottles = 99;
instance->private_data = iptr;
return 0;
}
int driver_close(struct inode *devicefile, struct file *instance) {
if (instance->private_data)
kfree(instance->private_data);
return 0;
}
static struct file_operations fops = {
.owner = THIS_MODULE,
.open = driver_open,
.release = driver_close,
.read = driver_read,
};
static int __init __init_module(void) {
if(register_chrdev(DRIVER_MAJOR, "99 Bottles of Beer", &fops) == 0)
return 0;
return -EIO;
}
static void __exit __cleanup_module(void) {
unregister_chrdev(DRIVER_MAJOR, "99 Bottles of Beer");
}
module_init(__init_module);
module_exit(__cleanup_module);
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Alternative Versions
| Version | Author | Date | Comments | Rate |
|---|---|---|---|---|
| actually produces correct lyrics :P | Dustshine | 08/20/05 | 0 | |
| Correct ANSI C containing no semicolons | Steve Checkoway | 01/15/09 | 0 | |
| multithreaded version | Stefan Scheler | 05/11/05 | 4 | |
| poor Style | Matteo Casati | 09/01/05 | 6 | |
| standard version | Bill Wein | 04/20/05 | 4 | |
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Comments
if (b==1)
strcat(buf, "no more bottles of beer on the wall.\n"
else {
sprintf(line, "%d bottle%s of beer on the wall.\n", b-1, PLURALS);
strcat(buf, line);printk("size %d\n", sizeof(struct _instance_data *));
}
print
"1 bottles of beer on the wall."
since b=2, so b-1 = 1, but the PLURALS macro uses b.
#include <stdio.h> int main(){int i=100;while(--i){printf("%i bottle%s of beer in the wall,\n%i bottle%s of beer.\nTake one down, p" "ass it round,\n""%s%s\n\n",i,i?"s":"",i,i?"s":"",(i-1)?(char[]){(((i-1)/10)?((i-1)/10+'0'):((i-1)%10+'0')),(((i- 1)/10)?((i-1)%10+'0'):' '),(((i-1)/10)?' ':'{TEXT}'),'{TEXT}'}:"",(i-1)?"bottles of beer in the wall":"No more beers");}}#include <stdio.h> int main(){int i=100;while(--i){printf("%i bottle%s of beer in the wall,\n%i bo" "ttle%s of beer.\nTake one down, pass it round,\n""%s%s\n\n",i,i?"s":"",i,i?"s": "",(i-1)?(char[]){(((i-1)/10)?((i-1)/10+'0'):((i-1)%10+'0')),(((i-1)/10)?((i-1)% 10+'0'):' '),(((i-1)/10)?' ':'{TEXT}'),'{TEXT}'}:"",(i-1)?"bottles of beer in the wall": "No more beers");}}<pre>
ifneq ($(KERNELRELEASE),)
obj-m := beer.o
else
KDIR := /lib/modules/$(shell uname -r)/build
PWD := $(shell pwd)
default:
$(MAKE) -C $(KDIR) SUBDIRS=$(PWD) modules
endif
</pre>
C is an Uncommon language
This couldn't be much shorter because it's kernel module.
C is uncommon?! That is so wrong! :D
C will never die!