Allocate a 3D char array in C (char ***) - c

Question

I would like to allocate a char***.
I have a got a sentence like this: "This is a command && which I || need to ; split"
I need to put in each box a full sentence just like that:
cmd[0] = "This is a command"
cmd[1] = "wich I"
cmd[2] = "need to"
cmd[3] = "split"
Sentences are separated by tokens like &&, ||, ;, |.
My problem is that I don't know how to allocate my triple dimension array.
I always get a Segmentation Fault.
This is what I do :
for(k = 0; k < 1024; k++)
for( j = 0; j < 1024; j++)
cmd[k][j] = malloc(1024);
But a few line later, in an other loop :
» cmd[k][l] = array[i];
I get a segfault here.
How can I do this please ?
Thanks in advance

Answer 1

Please keep in mind that a 2/3D array in C is not the same as a char ***.
If all you wish is to have a 1024^3 character array then you will be good with
char array[1024][1024][1024];
But keep in mind that this will allocate 1 GB of space on your stack which may or may not work.
To allocate this much on the heap you need to type it correctly:
char (*array)[1024][1024] = malloc(1024*1024*1024);
In this scenario array is a pointer to an array of 2D 1024x1024 character matrices.
If you really want to work with char *** (which I do not recommend if your array lengths are static) then you need to allocate all intermediary arrays too:
char *** cmd = malloc(sizeof(char **) * 1024);
for(k = 0; k < 1024; k++) {
cmd[k] = malloc(sizeof(char *) * 1024);
for( j = 0; j < 1024; j++)
cmd[k][j] = malloc(1024);
}

Answer 2

If you are going to be splitting your string by delimiters that are longer then a single character then this is how you could do it with string search.
The following function will accept an input string and a delimiter string.
It will return a char ** which has to be freed and it will destroy your input string (reusing it's memory to store the tokens).
char ** split_string(char * input, const char * delim) {
size_t num_tokens = 0;
size_t token_memory = 16; // initialize memory initially for 16 tokens
char ** tokens = malloc(token_memory * sizeof(char *));
char * found;
while ((found = strstr(input, delim))) { // while a delimiter is found
if (input != found) { // if the strind does not start with a delimiter
if (num_tokens == token_memory) { // increase the memory array if it is too small
void * tmp = realloc(tokens, (token_memory *= 2) * sizeof(char *));
if (!tmp) {
perror("realloc"); // out of memory
}
tokens = tmp;
}
tokens[num_tokens++] = input;
*found = '\0';
}
// trim off the processed part of the string
input = found + strlen(delim);
}
void * tmp = realloc(tokens, (num_tokens +1) * sizeof(char *));
if (!tmp) {
perror("realloc"); // something weird happened
}
tokens = tmp;
// this is so that you can count the amount of tokens you got back
tokens[num_tokens] = NULL;
return tokens;
}
You will need to recursively run this to split by more then one delimiter.