如何读取Linux键值，输入子系统，key，dev/input/event，dev/event，C语言键盘【转】

转自：https://blog.csdn.net/lanmanck/article/details/8423669

相信各位使用嵌入式的都希望直接读取键值，特别是芯片厂家已经提供input驱动的情况下，例如GPIO或者扫描类型的键盘。那么在应用层如何通过C语言获取键值呢？

给兄弟们一个重量级的源码，看下面，大家拿去编译运行就知道怎么回事了，当然，可以使用select而不是while()来读取更好一点，留给各位去想象了：

注意：

#include<linux/input.h>

为内核源码的头文件，注意路径，一般为kernel/include/linux/input.h

ev.c:

1. /*
2. * Copyright 2002 Red Hat Inc., Durham, North Carolina.
3. *
4. * All Rights Reserved.
5. *
6. * Permission is hereby granted, free of charge, to any person obtaining
7. * a copy of this software and associated documentation files (the
8. * "Software"), to deal in the Software without restriction, including
9. * without limitation on the rights to use, copy, modify, merge,
10. * publish, distribute, sublicense, and/or sell copies of the Software,
11. * and to permit persons to whom the Software is furnished to do so,
12. * subject to the following conditions:
13. *
14. * The above copyright notice and this permission notice (including the
15. * next paragraph) shall be included in all copies or substantial
16. * portions of the Software.
17. *
18. * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
19. * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
20. * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
21. * NON-INFRINGEMENT. IN NO EVENT SHALL RED HAT AND/OR THEIR SUPPLIERS
22. * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
23. * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
24. * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
25. * SOFTWARE.
26. *
27. * This is a simple test program that reads from /dev/input/event*,
28. * decoding events into a human readable form.
29. */
30.  
31. /*
32. * Authors:
33. * Rickard E. (Rik) Faith <faith@redhat.com>
34. *
35. */
36.  
37. #include <stdio.h>
38. #include <stdlib.h>
39. #include <unistd.h>
40. #include <string.h>
41. #include <sys/types.h>
42. #include <fcntl.h>
43. #include <errno.h>
44. #include <time.h>
45. #include <linux/input.h>
46.  
47. struct input_event event;
48.  
49. int main(int argc, char **argv)
50. {
51. char name[64]; /* RATS: Use ok, but could be better */
52. char buf[256] = { 0, }; /* RATS: Use ok */
53. unsigned char mask[EV_MAX/8 + 1]; /* RATS: Use ok */
54. int version;
55. int fd = 0;
56. int rc;
57. int i, j;
58. char *tmp;
59.  
60. #define test_bit(bit) (mask[(bit)/8] & (1 << ((bit)%8)))
61.  
62. for (i = 0; i < 32; i++) {
63. sprintf(name, "/dev/input/event%d", i);
64. if ((fd = open(name, O_RDONLY, 0)) >= 0) {
65. ioctl(fd, EVIOCGVERSION, &version);
66. ioctl(fd, EVIOCGNAME(sizeof(buf)), buf);
67. ioctl(fd, EVIOCGBIT(0, sizeof(mask)), mask);
68. printf("%s ", name);
69. printf(" evdev version: %d.%d.%d ",
70. version >> 16, (version >> 8) & 0xff, version & 0xff);
71. printf(" name: %s ", buf);
72. printf(" features:");
73. for (j = 0; j < EV_MAX; j++) {
74. if (test_bit(j)) {
75. const char *type = "unknown";
76. switch(j) {
77. case EV_KEY: type = "keys/buttons"; break;
78. case EV_REL: type = "relative"; break;
79. case EV_ABS: type = "absolute"; break;
80. case EV_MSC: type = "reserved"; break;
81. case EV_LED: type = "leds"; break;
82. case EV_SND: type = "sound"; break;
83. case EV_REP: type = "repeat"; break;
84. case EV_FF: type = "feedback"; break;
85. }
86. printf(" %s", type);
87. }
88. }
89. printf(" ");
90. close(fd);
91. }
92. }
93.  
94. if (argc > 1) {
95. sprintf(name, "/dev/input/event%d", atoi(argv[1]));
96. if ((fd = open(name, O_RDWR, 0)) >= 0) {
97. printf("%s: open, fd = %d ", name, fd);
98. for (i = 0; i < LED_MAX; i++) {
99. event.time.tv_sec = time(0);
100. event.time.tv_usec = 0;
101. event.type = EV_LED;
102. event.code = i;
103. event.value = 0;
104. write(fd, &event, sizeof(event));
105. }
106.  
107. while ((rc = read(fd, &event, sizeof(event))) > 0) {
108. printf("%-24.24s.%06lu type 0x%04x; code 0x%04x;"
109. " value 0x%08x; ",
110. ctime(&event.time.tv_sec),
111. event.time.tv_usec,
112. event.type, event.code, event.value);
113. switch (event.type) {
114. case EV_KEY:
115. if (event.code > BTN_MISC) {
116. printf("Button %d %s",
117. event.code & 0xff,
118. event.value ? "press" : "release");
119. } else {
120. printf("Key %d (0x%x) %s",
121. event.code & 0xff,
122. event.code & 0xff,
123. event.value ? "press" : "release");
124. }
125. break;
126. case EV_REL:
127. switch (event.code) {
128. case REL_X: tmp = "X"; break;
129. case REL_Y: tmp = "Y"; break;
130. case REL_HWHEEL: tmp = "HWHEEL"; break;
131. case REL_DIAL: tmp = "DIAL"; break;
132. case REL_WHEEL: tmp = "WHEEL"; break;
133. case REL_MISC: tmp = "MISC"; break;
134. default: tmp = "UNKNOWN"; break;
135. }
136. printf("Relative %s %d", tmp, event.value);
137. break;
138. case EV_ABS:
139. switch (event.code) {
140. case ABS_X: tmp = "X"; break;
141. case ABS_Y: tmp = "Y"; break;
142. case ABS_Z: tmp = "Z"; break;
143. case ABS_RX: tmp = "RX"; break;
144. case ABS_RY: tmp = "RY"; break;
145. case ABS_RZ: tmp = "RZ"; break;
146. case ABS_THROTTLE: tmp = "THROTTLE"; break;
147. case ABS_RUDDER: tmp = "RUDDER"; break;
148. case ABS_WHEEL: tmp = "WHEEL"; break;
149. case ABS_GAS: tmp = "GAS"; break;
150. case ABS_BRAKE: tmp = "BRAKE"; break;
151. case ABS_HAT0X: tmp = "HAT0X"; break;
152. case ABS_HAT0Y: tmp = "HAT0Y"; break;
153. case ABS_HAT1X: tmp = "HAT1X"; break;
154. case ABS_HAT1Y: tmp = "HAT1Y"; break;
155. case ABS_HAT2X: tmp = "HAT2X"; break;
156. case ABS_HAT2Y: tmp = "HAT2Y"; break;
157. case ABS_HAT3X: tmp = "HAT3X"; break;
158. case ABS_HAT3Y: tmp = "HAT3Y"; break;
159. case ABS_PRESSURE: tmp = "PRESSURE"; break;
160. case ABS_DISTANCE: tmp = "DISTANCE"; break;
161. case ABS_TILT_X: tmp = "TILT_X"; break;
162. case ABS_TILT_Y: tmp = "TILT_Y"; break;
163. case ABS_MISC: tmp = "MISC"; break;
164. default: tmp = "UNKNOWN"; break;
165. }
166. printf("Absolute %s %d", tmp, event.value);
167. break;
168. case EV_MSC: printf("Misc"); break;
169. case EV_LED: printf("Led"); break;
170. case EV_SND: printf("Snd"); break;
171. case EV_REP: printf("Rep"); break;
172. case EV_FF: printf("FF"); break;
173. break;
174. }
175. printf(" ");
176. }
177. printf("rc = %d, (%s) ", rc, strerror(errno));
178. close(fd);
179. }
180. }
181. return 0;
182. }

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