目的：用c語言模擬鍵盤輸入，這里是按下NUMLOCK鍵，等待2秒后，再按一次。問題：如果不用sleep()函數，按1次或兩次NUMLOCK鍵的程序，看到的NUMLOCK燈的狀態與預期一致。當用了sleep()函數后，再運行程序，會看到NUMLOCK燈亮起，直至程序結束也不熄滅，這時再用手在鍵盤上隨便按一個鍵，NUMLOCK燈才熄滅。代碼：#include <linux/input.h>#include <time.h>#include <fcntl.h>#include <string.h>#include <errno.h>#include <stdio.h>#include <stdlib.h> #include <unistd.h>void simulate_key(int fd, unsigned int keycode, int keyvalue){struct input_event event;event.type = EV_KEY;event.code = keycode;event.value = keyvalue;gettimeofday(&event.time, 0);if (write(fd, &event, sizeof(event)) < 0) {printf("simulate key error\n");return;}elseprintf("simuate key %d, %d\n", keycode, keyvalue);}int main ( int argc, char *argv[] ){char *path = "/dev/input/event3";unsigned int key_code = KEY_NUMLOCK;if (argc >= 3) {path = argv[1];key_code = atoi(argv[2]);}else if (argc >= 2)path = argv[1];int fd_kbd = open(path, O_RDWR);if(fd_kbd <= 0) {printf("error open keyboard:%s\n", strerror(errno));return -1;}simulate_key(fd_kbd, key_code, 1);simulate_key(fd_kbd, key_code, 0);sleep(2);simulate_key(fd_kbd, key_code, 1);simulate_key(fd_kbd, key_code, 0);close(fd_kbd);return 0;} /* ---------- end of function main ---------- */運行結果：simuate key 69, 1simuate key 69, 0（此處燈已亮，程序停2秒）simuate key 69, 1simuate key 69, 0（此處程序已結束，燈仍亮）（隨便在鍵盤敲一個鍵，燈滅）