Copying the value of a pointer to another pointer - c

Question

I would like to copy the value stored in char *command to a char *command_copy, because I am performing tokenization on command but still would like to use the initial command (which is why I am creating a copy). The problem is that every time I try something, the whole program goes crazy and I just can't find where to start or what to do.
Here is my code:
int main(void)
{
init_ui();
hist_init(100);
char *command;
while (true) {
signal(SIGINT, SIG_IGN);
command = read_command();
if (command == NULL) {
break;
}
char *command_copy;
command_copy = (char *) malloc(1000);
memcpy(command_copy, command, sizeof(*command));
char *args[4096];
int tokens = 0;
char *next_tok = command;
char *curr_tok;
while((curr_tok = next_token(&next_tok, " \t\n\r")) != NULL) {
if(strncmp(curr_tok, "#", 1) == 0){
break;
}
args[tokens++] = curr_tok;
}
args[tokens] = NULL;
if(args[0] == NULL) {
continue;
}
hist_add(command);
int builtin_status = handle_builtins(tokens, args);
if(builtin_status == 0) {
continue;
}
pid_t child = fork();
if(child == -1){
perror("fork");
}
...
I would like the hist_add() function to take command_copy instead of command because command at that point in the code is only the first word of the whole initial command, and I would like hist_add() to have the whole (original) command.
read_command(void):
char *read_command(void)
{
if(scripting == true) {
ssize_t read_sz = getline(&line, &line_sz, stdin);
if(read_sz == -1){
perror("getline");
free(line);
return NULL;
}
line[read_sz - 1] = '\0';
return line;
}
else {
return readline(prompt_line());
}
}

Answer 1

To make a copy of a char* string - so long as that string is properly nul-terminated - you can use the strdup function. This, essentially, is a combination of malloc and strcpy.
So, you can use something like this:
while (looping) {
char* original = getstring();
char* copy = strdup(original);
// ...
// do whatever you want with "original" - "copy" is left alone!
//
free(copy); // When you're done, free the copy
}
The strdup call is equivalent to the following:
char* copy = malloc(strlen(original) + 1);
strcpy(copy, original);