#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <dirent.h>
#include <string.h>
#include <time.h>
#include <errno.h>

int ds18b20_get_temperature(float *temp);


int main(int argc, char *argv[])
{
	float       temp;

	if( ds18b20_get_temperature(&temp) < 0 )
	{
		printf("ERROR: ds18b20 get temprature failure\n");
		return 1;
	}

       	printf("DS19B20 get temperature: %f ℃\n", temp);
       	return 0;
}

int ds18b20_get_temperature(float *temp)
{
    char            w1_path[50] = "/sys/bus/w1/devices/";
    char            chip[20];
    char            buf[128];
    DIR            *dirp;
    struct dirent  *direntp;
    int             fd =-1;
    char           *ptr;
    float           value;
    int             found = 0;

    if( !temp )
    {
	    return -1;
    }

    if((dirp = opendir(w1_path)) == NULL)
    {
        printf("opendir error: %s\n", strerror(errno));
        return -2;
    }

    while((direntp = readdir(dirp)) != NULL)
    {
        if(strstr(direntp->d_name,"28-"))
        {
            strcpy(chip,direntp->d_name);
	    found = 1;
        }
    }
    closedir(dirp);

    if( !found )
    {
	    printf("Can not find ds18b20 in %s\n", w1_path);
	    return -3;
    }

    strncat(w1_path, chip, sizeof(w1_path));
    strncat(w1_path, "/w1_slave", sizeof(w1_path));

    if( (fd=open(w1_path, O_RDONLY)) < 0 ) 
    { 
	    printf("open %s error: %s\n", w1_path, strerror(errno)); 
	    return -4;
    } 
    
    if(read(fd, buf, sizeof(buf)) < 0)
    {
	    printf("read %s error: %s\n", w1_path, strerror(errno)); 
	    return -5;
    } 
    
    ptr = strstr(buf, "t=")+2;

    if( !ptr )
    {
	    printf("ERROR: Can not get temperature\n");
	    return -6;
    }

    *temp = atof(ptr)/1000;
   
    return 0;
}