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学习总结(69)——Mysql EXPLAIN 命令使用总结
查看>>
Mysql学习总结(6)——MySql之ALTER命令用法详细解读
查看>>
Mysql学习总结(70)——MySQL 优化实施方案
查看>>
Mysql学习总结(71)——MySQL 重复记录查询与删除总结
查看>>
Mysql学习总结(71)——数据库介绍(MySQL安装 体系结构、基本管理)再回顾
查看>>
Mysql学习总结(72)——MySQL 开发者开发,设计规范再总结
查看>>
Mysql学习总结(73)——MySQL 查询A表存在B表不存在的数据SQL总结
查看>>
Mysql学习总结(74)——慢SQL!压垮团队的最后一根稻草!
查看>>
Mysql学习总结(75)——并发量大、数据量大的互联网业务数据库设计军规
查看>>
Mysql学习总结(76)——MySQL执行计划(explain)结果含义总结
查看>>
Mysql学习总结(77)——温故Mysql数据库开发核心原则与规范
查看>>
Mysql学习总结(78)——MySQL各版本差异整理
查看>>
Mysql学习总结(79)——MySQL常用函数总结
查看>>
Mysql学习总结(7)——MySql索引原理与使用大全
查看>>
Mysql学习总结(80)——统计数据库的总记录数和库中各个表的数据量
查看>>
Mysql学习总结(81)——为什么MySQL不推荐使用uuid或者雪花id作为主键?
查看>>
Mysql学习总结(82)——MySQL逻辑删除与数据库唯一性约束如何解决?
查看>>
Mysql学习总结(83)——常用的几种分布式锁:ZK分布式锁、Redis分布式锁、数据库分布式锁、基于JDK的分布式锁方案对比总结
查看>>
Mysql学习总结(84)—— Mysql的主从复制延迟问题总结
查看>>
Mysql学习总结(85)——开发人员最应该明白的数据库设计原则
查看>>