Question

我正在使用XCode在C中创建命令行程序。在运行程序时，它最初会执行它应该执行的操作（询问我的文件路径）。但是，当我键入有效的和现有的文件路径时，它会给我以下错误：

Program received signal:  “EXC_BAD_ACCESS”. sharedlibrary apply-load-rules all (gdb)

我的程序中有两个警告，这两个警告都与strcat函数有关。警告是：

warning: implicit declaration of function 'strcat'

和

warning: incompatible implicit declaration of built-in function 'strcat'

我想知道为什么我的程序没有正常执行。

谢谢，麦克

我的代码发布在下面：

#include "stdlib.h"
int main (void)
{
   char *string1;
   printf("Type in your file path: ");
   scanf("%s", string1);
   char *string2 = "tar czvf YourNewFile.tar.gz ";
   strcat(string2, string1);
   system(string2);
}

可能与分配字符有关吗？

Answer 1

您忘了为string1分配空间，scanf不会为您分配内存，您必须自己这样做。此外，string2指向不可写内存并且没有足够的空间向string1添加strcat，因此即使您有char string2[] = "tar czvf YourNewFile.tar.gz ";，#include <stdio.h> /* printf, sprintf, fgets */ #include <string.h> /* strcat, strlen */ #include <stdlib.h> /* malloc */ #define TAR "tar czvf YourNewFile.tar.gz" int main(void) { char path[100] = { 0 }; /* Initialize to all 0 bytes. */ char *cmd; /* We'll allocate space for this later. */ int len; printf("Type in your file path: "); fgets(path, sizeof(path), stdin); /* Read at most 100 characters into path */ /* * Remove the trailing newline (if present). */ len = strlen(path); if(path[len - 1] == '\n') path[len - 1] = '\0'; /* * Allocate room for our command. */ cmd = malloc( strlen(TAR) /* Room for the base tar command. */ + 1 /* One more for the space. */ + strlen(path) /* Room for the path we read. */ + 1 /* One more for the final nul terminator. */ ); /* * You could also use a bunch of strcpy and strcat stuff for * this but sprintf is less noisy and safe as long as you've * properly allocated your memory. */ sprintf(cmd, "%s %s", TAR, path); /* * This is vulnerable to unpleasant things in `path` (such as spaces, * &, >, <, ...) but this will do as a learning exercise. In real life * you'd probably want to use fork and exec for this to avoid the * interface issues with the shell. */ system(cmd); /* * Free the memory we allocated. */ free(cmd); /* * You need a return value because of "int main(...)". Zero is * the standard "all's well" return value. */ return 0; }也会溢出。

这是一个注释版本的东西，它更接近你真正想要的东西：

{{1}}

如果我犯了任何一个错误，请告诉我。

您可以在上面的over here找到这些功能的参考资料。

Answer 2

检查这一行：

char *string1

和这一行：

scanf("%s", string1);

你还没有为string1声明一个大小，这意味着你总会得到一个错误，用这样的东西修复它：

char string1[100]

如果100是输入的最大长度。

或按字符阅读输入字符。

并且，要删除警告，请将#include "string.h"添加到#include语句所在的位置。

程序收到信号：“EXC_BAD_ACCESS”？

2 个答案: