如何讀取Linux索引值，輸入子系統，key，dev/input/event，dev/event，C語言鍵盤

相信各位使用嵌入式的都希望直接讀取索引值，特別是晶片廠家已經提供input驅動的情況下，例如GPIO或者掃描類型的鍵盤。那麼在應用程式層如何通過C語言擷取索引值呢。

給兄弟們一個重量級的源碼，看下面，大家拿去編譯運行就知道怎麼回事了，當然，可以使用select而不是while()來讀取更好一點，留給各位去想象了：

注意：

#include<linux/input.h>

為核心源碼的標頭檔，注意路徑，一般為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;}