procfs信息讀取實現案例

procfs信息讀取實現案例：

1. /**********************************************
2. * Author: [email protected]
3. * File name: proc_sample.c
4. * Description: create a file "proc_example" in the /proc,
5. * which allows read.
6. * Date: 2011-12-11
7. * Version: V1.0
8. *********************************************/
10. #include <linux/kernel.h> /* We're doing kernel work */
11. #include <linux/module.h> /* Specifically, a module */
12. #include <linux/proc_fs.h> /* Necessary because we use proc fs */
13. #include <asm/uaccess.h> /* for get_user and put_user */
15. #define MESSAGE_LENGTH 80
16. #define PROC_NAME "proc_sample"
18. unsigned int flag = 100;
20. static struct proc_dir_entry *proc_sample;
21. static struct proc_dir_entry *sample, *sample_r;
23. /**
24. * proc_read_data()
25. * @page - buffer to write the data in
26. * @start - where the actual data has been written in page
27. * @offset - same meaning as the read system call
28. * @count - same meaning as the read system call
29. * @eof - set if no more data needs to be returned
30. * @data - pointer to our soft state
31. */
32. static int proc_read_data(char *page, char **stat, off_t off,
33. int count, int *eof, void *data)
34. {
35. int len;
36. len = sprintf(page, "jiffies = %ld\n", jiffies);
37. return len;
38. }
40. /*
41. * 模塊初始化
42. */
43. static int __init sample_init(void)
44. {
45. int ret = 0;
47. /*
48. * proc_mkdir(name, parent)
49. * 在parent對應的目錄下創建name目錄
50. * 返回目錄對應的proc_dir_dentry
51. */
52. proc_sample = proc_mkdir(PROC_NAME, NULL);
53. if (NULL == proc_sample) {
54. ret = -ENOMEM;
55. goto proc_sample_err;
56. }
57. /*
58. * create_proc_entry(name, mode,parent)
59. * 在parent對應的目錄下創建name文件
60. * 返回目錄對應的proc_dir_dentry
61. */
62. sample = create_proc_entry("sample", 0644, proc_sample);
63. if (NULL == sample) {
64. ret = -ENOMEM;
65. goto sample_err;
66. }
68. sample_r = create_proc_read_entry("sample_r", 0444,
69. proc_sample, proc_read_data, NULL);
70. if (NULL == sample_r) {
71. ret = -ENOMEM;
72. goto sample_r_err;
73. }
75. printk(KERN_INFO "Create sample\n");
76. return ret;
78. sample_r_err:
79. remove_proc_entry("sample", proc_sample);
80. sample_err:
81. remove_proc_entry(PROC_NAME, NULL);
82. proc_sample_err:
83. return ret;
84. }
86. /*
87. * 模塊清理
88. */
89. static void __exit sample_exit(void)
90. {
91. remove_proc_entry("sample", proc_sample);
92. remove_proc_entry("sample_r", proc_sample);
93. remove_proc_entry(PROC_NAME, NULL);
94. printk(KERN_INFO "Remove /proc/proc_sample\n");
95. }
97. module_init(sample_init);
98. module_exit(sample_exit);
99. MODULE_LICENSE("GPL");
100. MODULE_AUTHOR("lewiyon <[email protected]>");

在/proc/創建文件目錄proc_sampe，然後在其下創建了兩個文件。其中sample_r可讀取數據