C: creating array of strings from delimited source string

Question

What would be an efficient way of converting a delimited string into an array of strings in C (not C++)? For example, I might have:

char *input = \"valgrind         


        

Answer 1

if you have all of the input in input to begin with then you can never have more tokens than strlen(input). If you don't allow "" as a token, then you can never have more than strlen(input)/2 tokens. So unless input is huge you can safely write.

char ** myarray = malloc( (strlen(input)/2) * sizeof(char*) );

int NumActualTokens = 0;
while (char * pToken = get_token_copy(input))
{ 
   myarray[++NumActualTokens] = pToken;
   input = skip_token(input);
}

char ** myarray = (char**) realloc(myarray, NumActualTokens * sizeof(char*));

As a further optimization, you can keep input around and just replace spaces with \0 and put pointers into the input buffer into myarray[]. No need for a separate malloc for each token unless for some reason you need to free them individually.