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日志文件
查看>>
mysql日志管理学习笔记
查看>>
mysql日志问题定位实用命令
查看>>
MySQL日期时间函数大全
查看>>
mysql时间相减的问题
查看>>
mysql时间表示和计算
查看>>
MySQL是如何做容器测试的?
查看>>
mysql更改数据库表utf-8_修改mysql数据库为 utf-8
查看>>
mysql更改表引擎INNODB为MyISAM的方法总结
查看>>
mysql更新一个表里的字段等于另一个表某字段的值
查看>>
Mysql更新时间列只改日期为指定日期不更改时间
查看>>
MySQL更新锁(for update)摘要
查看>>
mysql更新频率_MySQL优化之如何了解SQL的执行频率
查看>>
mysql替换表的字段里面内容
查看>>
MySQL最多能有多少连接
查看>>
MySQL最大建议行数 2000w,靠谱吗?
查看>>
MySQL有哪些锁
查看>>
MySQL服务器安装(Linux)
查看>>
mysql服务器查询慢原因分析方法
查看>>
mysql服务无法启动的问题
查看>>