博客
关于我
C语言中函数strcpy ,strncpy ,strlcpy的用法
阅读量:670 次
发布时间:2019-03-16

本文共 2995 字,大约阅读时间需要 9 分钟。

safe string copying in C: safer strncpy vs strlcpy and more

In C programming,edeックス predecessor言下之意[a function is as important as the programmer who uses it[/Vetaのリスト]. For string manipulation,.AutoSize experts rely on functions like strcpy, strncpy, memcpy, and recently strlcpy to avoid buffer overflow issues while copying data. Among these, strlcpy sometimes be [eve

from the dinosaurs to the modern era: the journey of string copying functions

Developers have long debated which function to use for saffer and safer string copying. Back in the day, strcpy was the only option, and it was dangerous because it assumed the destination buffer had enough space and was properly terminated with a null byte /0. This assumption often led to buffer overflowattacks when dealing with untrusted user input.

the rise of strncpy: a safer alternative

Ansic standard introduced strncpy as a safer alternative. The function copies up to n bytes from the source string to the destination buffer, but it has some quirky behaviors. For example, if the source string is shorter than n, strncpy fills the destination with null bytes until the end of the n bytes. This can be useful in some cases but feels counterintuitive compared to how strcpy works.

the better choice: strlcpy

Like many open-source projects, OpenBSD developers created strlcpy to address the shortcomings of strncpy. The function ensures that the destination buffer is properly null-terminated and does not overwrite beyond the buffer's capacity. If the source string is longer than the destination buffer, the excess data is discarded, and the function returns the original length of the source string to help detect truncation.

Why Use strlcpy Instead of strncpy?

  • No Need for Manual Null Termination: With strlcPy, you simply provide the size of the destination buffer and let the function handle the rest.
  • Always Null-Terminated: The function ensures the destination buffer is properly terminated with a null byte, even if the source string is shorter than the destination.
  • Return Value for檢查: strlcpy returns the length of the source string, allowing you to detect if the copy operation was truncated.

cross-platform considErsations

While strlCpY is a great choice for Unix-like systems, it's not part of the C standard. Windows, for example, doesn't have a native strlCpY function, and the process of copying strings often involves using strncpy combined with memset to clear the remaining buffer.

when to use memcpy?

memcpy is a lower-level function that directly copies bytes without any assumptions about the source or destination data. It's useful for copying arbitrary data, including binary data that may contain null bytes. However, it requires careful buffer management to prevent overruns.

conclusion

In modern C programming, strlCpY is often the best choice for both saffer and efficient string operations. However, your choice of function depends on the specific needs of your project and the environments you're targeting.

转载地址:http://xnoqz.baihongyu.com/

你可能感兴趣的文章
mysql client library_MySQL数据库之zabbix3.x安装出现“configure: error: Not found mysqlclient library”的解决办法...
查看>>
MySQL Cluster 7.0.36 发布
查看>>
Multimodal Unsupervised Image-to-Image Translation多通道无监督图像翻译
查看>>
MySQL Cluster与MGR集群实战
查看>>
multipart/form-data与application/octet-stream的区别、application/x-www-form-urlencoded
查看>>
mysql cmake 报错,MySQL云服务器应用及cmake报错解决办法
查看>>
Multiple websites on single instance of IIS
查看>>
mysql CONCAT()函数拼接有NULL
查看>>
multiprocessing.Manager 嵌套共享对象不适用于队列
查看>>
multiprocessing.pool.map 和带有两个参数的函数
查看>>
MYSQL CONCAT函数
查看>>
multiprocessing.Pool:map_async 和 imap 有什么区别?
查看>>
MySQL Connector/Net 句柄泄露
查看>>
multiprocessor(中)
查看>>
mysql CPU使用率过高的一次处理经历
查看>>
Multisim中555定时器使用技巧
查看>>
MySQL CRUD 数据表基础操作实战
查看>>
multisim变压器反馈式_穿过隔离栅供电:认识隔离式直流/ 直流偏置电源
查看>>
mysql csv import meets charset
查看>>
multivariate_normal TypeError: ufunc ‘add‘ output (typecode ‘O‘) could not be coerced to provided……
查看>>