From 732d1963ed83abf4e5f1b06ec451a6943421d716 Mon Sep 17 00:00:00 2001
From: Guo Wenxue <guowenxue@gmail.com>
Date: Thu, 22 Sep 2022 00:36:11 +0800
Subject: [PATCH] update ds18b20.c to snprintf
---
apue/1.File_IO/ds18b20.c | 73 +++++++++++++++++++-----------------
1 files changed, 39 insertions(+), 34 deletions(-)
diff --git a/apue/1.File_IO/ds18b20.c b/apue/1.File_IO/ds18b20.c
index d170de1..0ff2a34 100644
--- a/apue/1.File_IO/ds18b20.c
+++ b/apue/1.File_IO/ds18b20.c
@@ -1,14 +1,14 @@
/*********************************************************************************
- * Copyright: (C) 2018 LingYun IoT System Studio
+ * Copyright: (C) 2022 LingYun IoT System Studio
* All rights reserved.
*
* Filename: ds18b20.c
- * Description: This file is temperature sensor DS18B20 code
- *
+ * Description: This file is DS18B20 temperature sensor example source code.
+ *
* Version: 1.0.0(2018/10/14)
* Author: Guo Wenxue <guowenxue@gmail.com>
* ChangeLog: 1, Release initial version on "2018/10/14 12:13:26"
- *
+ *
********************************************************************************/
#include <stdio.h>
@@ -24,40 +24,41 @@
int main(int argc, char *argv[])
{
- float temp;
+ float temp;
- if( ds18b20_get_temperature(&temp) < 0 )
- {
- printf("ERROR: ds18b20 get temprature failure\n");
- return 1;
- }
+ if( ds18b20_get_temperature(&temp) < 0 )
+ {
+ printf("ERROR: ds18b20 get temprature failure\n");
+ return 1;
+ }
- printf("DS19B20 get temperature: %f ℃\n", temp);
- return 0;
+ printf("DS18B20 get temperature: %f 'C\n", temp);
+ return 0;
}
/* File Content:
- pi@raspberrypi:~/guowenxue $ cat /sys/bus/w1/devices/28-041731f7c0ff/w1_slave
+ pi@raspberrypi:~/guowenxue $ cat /sys/bus/w1/devices/28-041731f7c0ff/w1_slave
3a 01 4b 46 7f ff 0c 10 a5 : crc=a5 YES
3a 01 4b 46 7f ff 0c 10 a5 t=19625
*/
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;
if( !temp )
{
- return -1;
+ return -1;
}
/*+-------------------------------------------------------------------+
@@ -76,44 +77,48 @@
/* find and get the chipset SN filename */
strcpy(chip,direntp->d_name);
found = 1;
+ break;
}
}
closedir(dirp);
if( !found )
{
- printf("Can not find ds18b20 in %s\n", w1_path);
- return -3;
+ printf("Can not find ds18b20 in %s\n", w1_path);
+ return -3;
}
/* 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 )
- {
- printf("open %s error: %s\n", w1_path, strerror(errno));
- return -4;
- }
-
+ if( (fd=open(ds_path, O_RDONLY)) < 0 )
+ {
+ 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));
- return -5;
- }
-
+ printf("read %s error: %s\n", ds_path, strerror(errno));
+ rv = -5;
+ goto cleanup;
+ }
+
ptr = strstr(buf, "t=");
if( !ptr )
{
- printf("ERROR: Can not get temperature\n");
- return -6;
+ printf("ERROR: Can not get temperature\n");
+ rv = -6;
+ goto cleanup;
}
ptr+=2;
/* convert string value to float value */
*temp = atof(ptr)/1000;
-
- return 0;
+
+cleanup:
+ close(fd);
+ return rv;
}
--
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