update led and gpio program

guowenxue

2021-11-03 1a128c78e4119cae8d35b661149a12d0fd083b1a

 apue/1.File_IO/ds18b20.c

@@ -116,5 +116,7 @@
    /* convert string value to float value */
    *temp = atof(ptr)/1000;
   
    close(fd);

    return 0;
}