如何在 argv[] 中使用作为命令行参数传递的字符串填充新数组？

Question

我对编码比较陌生，尤其是在 C 语言中。我正在尝试创建一个简单的程序，旨在将短语或字符串列表作为填充 char* argv[] 的命令行参数。然后，我想对每个字符执行基于 ASCII 的简单更改（例如使 a => b、b => c、... z => a 等），然后用更改后的字符串填充一个新数组。本质上，新对象将是一个字符数组，就像我相信 argv[] 一样。

这是我的代码，虽然我被各种“指针不兼容的转换赋值**char to string int char variable.....Segmentation fault”样式错误轰炸。

#include <stdio.h>  
#include <string.h>  


int main(int argc, char* argv[])  
{  
    
    char* cipher[argc];  
    for (int i = 1; i < argc; i++)  
    {  
        int n = strlen(argv[i]);  
        for (int j = 0; j < n-1; j++)  
        {  
            cipher[i][j] = argv[i][j];  
        }  
    }  
    for (int i = 0; i<argc-1; i++)  
    {  
        printf("%s\n", cipher[i]);  
    }  
}  

代码将通过命令行运行如下：

./secret the man in the middle is guilty

然后返回一个加扰的形式。我省略了加扰算法，因为这不是我遇到的问题。

我知道我可以更轻松地创建打印更改消息的代码，但我希望能够将新消息存储在数组中以防进一步更改。我不明白为什么我不能只访问特定二维索引的字符值并用它们填充新的“密码”数组。

我不明白什么？

Answer 1

一堆问题：

#include <stdio.h>  
#include <string.h>  


int main(int argc, char* argv[])  
{  
    

    // first issue: this is only allocating space for "pointers" to
    // strings [argc many] but no space for actual strings so you have to 
    // allocate them.


    // also this is only really workable with c99 (assuming that's the case)
    char* cipher[argc];  

    // this is okay 
    for (int i = 1; i < argc; i++)  
    {  

       // this is where you would allocate space and 
       // perform the copy
        int n = strlen(argv[i]);  
        for (int j = 0; j < n-1; j++)  
        {  
            cipher[i][j] = argv[i][j];  
        }  
    }

   
    for (int i = 0; i<argc-1; i++)  
    {  
        printf("%s\n", cipher[i]);  
    }  
}  

所以至少最低限度：

#include <stdio.h>
#include <string.h> 

int main(int argc, char* argv[])  
{  
   
    char* cipher[argc];

    // this is okay 
    for (int i = 1; i < argc; i++)  
    {  
         // strdup will return a newly allocated copy
         // and since cipher[] is an array of pointers 
         // you are good to go.
         cipher[i-1] = strdup(argv[i]);
    }

   
    for (int i = 0; i<argc-1; i++)  
    {  
        printf("%s\n", cipher[i]);  
    }  

    // later on after you are finished with cipher 
    // assuming that you still have other things to do
    // you can de-allocate the memory (although not sure if
    // that will be required)

    for(int i = 0; i < argc - 1; i++) {
         free(cipher[i]); // strdup allocated memory cleanup
    }

    // you can no longer use cipher[i] here because it's contents
    // have been destroyed by the free above.
}