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:
/*
* Copyright 2002 Red Hat Inc., Durham, North Carolina.
*
* All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation on the rights to use, copy, modify, merge,
* publish, distribute, sublicense, and/or sell copies of the Software,
* and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice (including the
* next paragraph) shall be included in all copies or substantial
* portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NON-INFRINGEMENT. IN NO EVENT SHALL RED HAT AND/OR THEIR SUPPLIERS
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*
* This is a simple test program that reads from /dev/input/event*,
* decoding events into a human readable form.
*/
/*
* Authors:
* Rickard E. (Rik) Faith <faith@redhat.com>
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <fcntl.h>
#include <errno.h>
#include <time.h>
#include <linux/input.h>
struct input_event event;
int main(int argc, char **argv)
{
char name[64]; /* RATS: Use ok, but could be better */
char buf[256] = { 0, }; /* RATS: Use ok */
unsigned char mask[EV_MAX/8 + 1]; /* RATS: Use ok */
int version;
int fd = 0;
int rc;
int i, j;
char *tmp;
#define test_bit(bit) (mask[(bit)/8] & (1 << ((bit)%8)))
for (i = 0; i < 32; i++) {
sprintf(name, "/dev/input/event%d", i);
if ((fd = open(name, O_RDONLY, 0)) >= 0) {
ioctl(fd, EVIOCGVERSION, &version);
ioctl(fd, EVIOCGNAME(sizeof(buf)), buf);
ioctl(fd, EVIOCGBIT(0, sizeof(mask)), mask);
printf("%s\n", name);
printf(" evdev version: %d.%d.%d\n",
version >> 16, (version >> 8) & 0xff, version & 0xff);
printf(" name: %s\n", buf);
printf(" features:");
for (j = 0; j < EV_MAX; j++) {
if (test_bit(j)) {
const char *type = "unknown";
switch(j) {
case EV_KEY: type = "keys/buttons"; break;
case EV_REL: type = "relative"; break;
case EV_ABS: type = "absolute"; break;
case EV_MSC: type = "reserved"; break;
case EV_LED: type = "leds"; break;
case EV_SND: type = "sound"; break;
case EV_REP: type = "repeat"; break;
case EV_FF: type = "feedback"; break;
}
printf(" %s", type);
}
}
printf("\n");
close(fd);
}
}
if (argc > 1) {
sprintf(name, "/dev/input/event%d", atoi(argv[1]));
if ((fd = open(name, O_RDWR, 0)) >= 0) {
printf("%s: open, fd = %d\n", name, fd);
for (i = 0; i < LED_MAX; i++) {
event.time.tv_sec = time(0);
event.time.tv_usec = 0;
event.type = EV_LED;
event.code = i;
event.value = 0;
write(fd, &event, sizeof(event));
}
while ((rc = read(fd, &event, sizeof(event))) > 0) {
printf("%-24.24s.%06lu type 0x%04x; code 0x%04x;"
" value 0x%08x; ",
ctime(&event.time.tv_sec),
event.time.tv_usec,
event.type, event.code, event.value);
switch (event.type) {
case EV_KEY:
if (event.code > BTN_MISC) {
printf("Button %d %s",
event.code & 0xff,
event.value ? "press" : "release");
} else {
printf("Key %d (0x%x) %s",
event.code & 0xff,
event.code & 0xff,
event.value ? "press" : "release");
}
break;
case EV_REL:
switch (event.code) {
case REL_X: tmp = "X"; break;
case REL_Y: tmp = "Y"; break;
case REL_HWHEEL: tmp = "HWHEEL"; break;
case REL_DIAL: tmp = "DIAL"; break;
case REL_WHEEL: tmp = "WHEEL"; break;
case REL_MISC: tmp = "MISC"; break;
default: tmp = "UNKNOWN"; break;
}
printf("Relative %s %d", tmp, event.value);
break;
case EV_ABS:
switch (event.code) {
case ABS_X: tmp = "X"; break;
case ABS_Y: tmp = "Y"; break;
case ABS_Z: tmp = "Z"; break;
case ABS_RX: tmp = "RX"; break;
case ABS_RY: tmp = "RY"; break;
case ABS_RZ: tmp = "RZ"; break;
case ABS_THROTTLE: tmp = "THROTTLE"; break;
case ABS_RUDDER: tmp = "RUDDER"; break;
case ABS_WHEEL: tmp = "WHEEL"; break;
case ABS_GAS: tmp = "GAS"; break;
case ABS_BRAKE: tmp = "BRAKE"; break;
case ABS_HAT0X: tmp = "HAT0X"; break;
case ABS_HAT0Y: tmp = "HAT0Y"; break;
case ABS_HAT1X: tmp = "HAT1X"; break;
case ABS_HAT1Y: tmp = "HAT1Y"; break;
case ABS_HAT2X: tmp = "HAT2X"; break;
case ABS_HAT2Y: tmp = "HAT2Y"; break;
case ABS_HAT3X: tmp = "HAT3X"; break;
case ABS_HAT3Y: tmp = "HAT3Y"; break;
case ABS_PRESSURE: tmp = "PRESSURE"; break;
case ABS_DISTANCE: tmp = "DISTANCE"; break;
case ABS_TILT_X: tmp = "TILT_X"; break;
case ABS_TILT_Y: tmp = "TILT_Y"; break;
case ABS_MISC: tmp = "MISC"; break;
default: tmp = "UNKNOWN"; break;
}
printf("Absolute %s %d", tmp, event.value);
break;
case EV_MSC: printf("Misc"); break;
case EV_LED: printf("Led"); break;
case EV_SND: printf("Snd"); break;
case EV_REP: printf("Rep"); break;
case EV_FF: printf("FF"); break;
break;
}
printf("\n");
}
printf("rc = %d, (%s)\n", rc, strerror(errno));
close(fd);
}
}
return 0;
}