I.MX6 Android(安卓)backlight modify by C demo

/************************************************************************** *             I.MX6 Android backlight modify by C demo * 说明： *     因为一些特殊情况，需要添加一个这个简单的控制程序来控制android背光 * 亮度，个人感觉是没有必要的，但是应要求还是加上。 * *                                      2016-5-14 深圳 南山平山村 曾剑锋 *************************************************************************/#include <stdio.h>  #include <stdlib.h>  #include <unistd.h>  #include <sys/types.h>  #include <sys/stat.h>  #include <fcntl.h>      #include <termios.h>    #include <string.h>#include <errno.h>  #define BACKLIGHT0_PATH "/sys/class/backlight/pwm-backlight.0/brightness"#define BACKLIGHT1_PATH "/sys/class/backlight/pwm-backlight.1/brightness"//#define BACKLIGHT0_PATH "brightness0"//#define BACKLIGHT1_PATH "brightness1"int help ( int argc );int isDigitalStr(char *str);int file_exists(char *filename);void writeStringToFile(char *filePath, char *string);int main(int argc, char **argv)  {      int bl0 = 0;    int bl1 = 0;        if ( help( argc ) != 0)        return -1;    if ( !isDigitalStr(argv[1]) ) {        printf("Please give a numeric string.\n");        return -1;    }       writeStringToFile(BACKLIGHT0_PATH, argv[1]);    writeStringToFile(BACKLIGHT1_PATH, argv[1]);}void writeStringToFile(char *filePath, char *string) {    int fd = 0;    if ( file_exists(filePath) ) {        fd = open(filePath, O_RDWR);        ftruncate(fd, 0);        write(fd, string, strlen(string));        close(fd);    }}int isDigitalStr(char *str){       int len = strlen(str);    char *s = str;    int i = 0;     while( '0' <= *s && *s <= '9' && i < len){        s++;        i++;    }    if(i == len)        return 1;    else         return 0;       }int file_exists(char *filename) {     if (access(filename, F_OK) == 0) {        return 1;    } else {        printf("%s is not exist.\n", filename);        return 0;    }}int help( int argc ) {    if ( argc != 2 ) {        printf ( "USAGE:\n" );        printf ( "    backlight <value>\n" );        printf ( "    example:\n" );        printf ( "        backlight 0\n" );        return -1;    }    return 0;}
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