将字符串数组复制到另一个字符串数组 - C

Question

我有一个包含字符串数组（char **args）的结构。我需要能够将字符串数组 (char *input[32]) 复制到结构的该元素中。例如：

Thing s;
s.args = input; //assuming input already has some strings in it

当我尝试这样做时，下次调用 s.args = input 时，它会完全覆盖旧输入。如何以适当的方式实现此功能？

编辑

这就是结构的样子。

typedef struct{
char **args;
} Thing;

然后在我的函数中，我声明：

char *args[512];
.....
args[count] = string //string is a char *

最后，我想做：

s.args = input.

Answer 1

你不是在复制它。您实际上只是设置指针。实际上你有这个：

char **args;
char *other[32];
args = other;

You need to actually copy the array - for that you need to allocate memory for it:

s.args = malloc( 32 * sizeof(char*) );

for( i = 0; i < 32; i++ ) s.args[i] = input[i];

That is a shallow copy - it will copy your string pointers but not duplicate them. If you change the contents of a string in input, that change will be reflected in s.args. To copy the strings, you must do this:

for( i = 0; i < 32; i++ ) s.args[i] = strdup(input[i]);

Since you have allocated memory, then before you overwrite s.args again (and also when your program is finished) you need to free what you allocated. This includes the strings (if you called strdup);

if( s.args != NULL ) {
    // Only do the loop if you did a deep copy.
    for( i = 0; i < 32; i++ ) free(s.args[i]);

    // Free the array itself
    free(s.args);
}