Problem making strings in a malloc-ed struct

[itsthemac]

I have a struct with the following definition:

struct node{
   char * name;
   struct node * next;
};

The problem is that I want to make a linked list of these nodes, each having its own name. These names are to come from standard input -- that is, they are not static. I can't figure out how to put a string into the "name" field of a dynamically allocated node so that it doesn't disintegrate when the function that it was created within completes execution. I'm pretty sure there's no way to malloc a string. Does anyone have any suggestions? I've been working on this one little problem for over 40 minutes.

[Subsonics]

Besides making name an array and make sure it's not overflown at input, you can also allocate memory for it separately.

Assuming the string, 'string' exists.

struct node *node = malloc(sizeof(struct node));
node->name = malloc(strlen(string)+1);

Edit: strdup() is a much better suited function to use here. Still, you could use this two step approach if you are creating nodes dynamically.

[anduril462]

You have to read it into a temporary buffer, then allocate space and copy:

char buf[100];
struct node n;

fgets(buf, sizeof(buf), stdin);
// clean up input, remove any new lines fgets leaves
n.name = strdup(buf);

This is a very simple example. It may run into problems if the user wants to enter more than 100 chars. You can make the buffer larger, or do a loop of fgets reads with malloc/realloc and strcpy if you need lots more space.

[Bayint Naung]

Take note that strdup() is non standard function.
Even though it's not hard to implement yourself.

Edit: strdup is in C99.

[itsthemac]

Thanks! I had no idea about strdup. For some reason I just assumed malloc-ing strings was a faux pas, but I couldn't see any other way around this problem. cheers

[anduril462]

Thanks! I had no idea about strdup. For some reason I just assumed malloc-ing strings was a faux pas, but I couldn't see any other way around this problem. cheers

I should have mentioned that strdup is not part of the standard. It's a proposed add-on to the C99 standard, thus you might not find it on all platforms/compilers. As a workaround, you can do what Subsonics suggested (with the obvious strcpy afterward).

[CommonTater]

Thanks! I had no idea about strdup. For some reason I just assumed malloc-ing strings was a faux pas, but I couldn't see any other way around this problem. cheers

Well, think about it... what is a string?
It is an array of characters. The only thing that makes it any different from any other array is the trailing 0 at the end.

Your first option is to use the array style declaration in your struct...

struct t_LList
  {  char text[100];
     t_LList* next; }

Also malloc() then strcpy() or strdup() (really just strcpy with malloc included) are perfectly legitimate ways of initializing a char* array as others have already shown you.