update ds18b20.c to snprintf

Guo Wenxue

2022-09-22 732d1963ed83abf4e5f1b06ec451a6943421d716

update ds18b20.c to snprintf

 apue/1.File_IO/ds18b20.c

@@ -45,14 +45,14 @@

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

@@ -89,19 +89,18 @@
    }

    /* get DS18B20 sample file full path: /sys/bus/w1/devices/28-xxxx/w1_slave */
    strncat(w1_path, chip, sizeof(w1_path)-strlen(w1_path));
    strncat(w1_path, "/w1_slave", sizeof(w1_path)-strlen(w1_path));
    snprintf(ds_path, sizeof(ds_path), "%s/%s/w1_slave", w1_path, chip);

    /* open file /sys/bus/w1/devices/28-xxxx/w1_slave to get temperature */
    if( (fd=open(w1_path, O_RDONLY)) < 0 )
    if( (fd=open(ds_path, O_RDONLY)) < 0 )
    {
        printf("open %s error: %s\n", w1_path, strerror(errno));
        printf("open %s error: %s\n", ds_path, strerror(errno));
        return -4;
    }

    if(read(fd, buf, sizeof(buf)) < 0)
    {
        printf("read %s error: %s\n", w1_path, strerror(errno));
        printf("read %s error: %s\n", ds_path, strerror(errno));
        rv = -5;
        goto cleanup;
    }