How do I assign an element of a 2-dimensional array?-CodePudding

I have a two-dimensional char array (an array of strings). When I try to assign a string to an element, an error occurs saying "array type 'char *[8]' is not assignable".

This is my code:

int main() {
    char *array[4][8];
    array[0] = "test";
}

How would I properly assign an element of a 2-D array?

CodePudding user response：

Maybe by using 2 dimensions of the 2D array. array[0][0] = "test;"

Though please note that in your case this is a 2D array of pointers to string literals. And since string literals are read-only, it should be declared as const char *array[4][8];. If you want read/write memory then you should assign the pointers to dynamically allocated memory instead.

CodePudding user response：

the error is may be beacuse you trspecifing row and not column of the array(remeber you are using 2D array).

Try this:

int main() {
    char *array[4][8];
    array[0][0] = "test";
}

CodePudding user response：

int main() { 
    char *array[4][8];
    array[0] = "test";
}

In the above code you first create a two-dimensional array of char*. The mistake occures on the second line. You are trying to assign a value to array[0], but since array is a two dimensional array array[0] doesn't point to a char*, instead it points to an array of char*. The correct way of doing this would be:

array[0][0] = "test";

This would assign the first element in the first array to "test".

CodePudding user response：

I have a two-dimensional char array (an array of strings).

This is my code: char *array[4][8];

That is not a two-dimensinal char array. It's a two-dimentional array of char pointers.

To get a two-dimentional char array that can be used as an array of strings do

char array[4][8];  // i.e. without *

Now you can save 4 strings with max length 7.

C has no way to assign a string using =. In C you can use strcpy to copy a string into your variable like:

strcpy(array[0], "test");

However, you can initialize the array with strings using = like:

char array[4][8] ={"test", "hello", "world", "done"};

and for instance print them like:

for (int i=0; i < 4;   i) puts(array[i]);

The output will be:

test
hello
world
done

The second dimension of the array can be used to access the individual characters of the strings. For instance:

printf("%c", array[1][4]);

will print the o from hello

CodePudding user response：

You need to use the correct array subscript. The type of array[0] is char *[8] but you need array[0][0] which is of type char *. Then you want to allocate a writable string with for example strdup():

#include <string.h>
// ...
char *array[4][8];
array[0][0] = strdup("test");
free(array[0][0]);

You could also change the type to const as you cannot change that string literal:

const char *array2[4][8];
array2[0][0] = "test";

Or perhaps you meant to copy the data into an an array:

#include <string.h>
//...
char array3[4][8];
strcpy(array3[0], "test");