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文字

在头文件<stdio.h>中定义



char * gets(char * str);


(直到C11)

char * gets_s(char * str,rsize_t n);


(自C11以来)(可选)

1)读stdin入指向的字符数组,str直到找到换行符或发生文件结束。在读入数组的最后一个字符后立即写入空字符。换行符被丢弃,但不存储在缓冲区中。

2)读取字符,stdin直到找到换行符或发生文件结束。只将大部分n-1字符写入指向的数组中str,并始终写入终止空字符(除非str是空指针)。换行符(如果找到)将被丢弃,并且不计入写入缓冲区的字符数。在运行时检测到以下错误并调用当前安装的约束处理函数:

  • n 是零

  • n 大于 RSIZE_MAX

  • str 是一个空指针

  • n-1字符存储到缓冲区后,不会遇到endline或eof 。

无论如何,在调用约束处理程序之前,gets_s首先完成读取和放弃字符,stdin直到换行符,文件结束条件或读取错误。作为所有边界检查函数,gets_s只有在被__STDC_LIB_EXT1__实现定义__STDC_WANT_LIB_EXT1__并且1在包含之前用户定义为整数常量时才能保证可用<stdio.h>

参数

str

-

要写入的字符串

返回值

str成功时,NULL失败。

如果失败是由文件结束条件引起的,则另外设置eof指示符(参见feof()stdin。如果故障是由其他错误引起的,请设置错误指示器(参见ferror()stdin

注意

gets()函数不执行边界检查,因此该函数极易受缓冲区溢出攻击的影响。它不能安全使用(除非程序在限制可能出现的内容的环境中运行stdin)。出于这个原因,该功能在C99标准的第三勘误中已被弃用,并在C11标准中完全删除。fgets()并且gets_s()是推荐的替代品。

切勿使用 gets()**。**

参考

  • C11标准(ISO / IEC 9899:2011):

    • K.3.5.4.1 gets_s函数(p:602-603)

  • C99标准(ISO / IEC 9899:1999):

    • 7.19.7.7 gets函数(p:298)

  • C89 / C90标准(ISO / IEC 9899:1990):

    • 4.9.7.7获取函数

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