Reading and Concatenating Strings

[FallenBlade]

I have a main method that creates a String and passes it to a function:

char* user_command;

user_command = get_user_command(user_command);

Then the function "get_user_command" finds out what the user wants to do in my program and sends back a String containing the command.

char* get_user_command(char* user_command)
{
	int choice;
	char text[20];

	printf("-=Security Station=-\n");
	printf("Add a User 	[1]\n");
	printf("Change Type 	[2]\n");
	printf("Change Location [3]\n");
	printf("Remove User 	[4]\n");

	   fputs("Choice: ", stdout);
	   fflush(stdout);
	   if ( fgets(text, sizeof text, stdin) )
	   {
	      if ( sscanf(text, "%d", &choice) == 1 )
	      {
	         printf("number = %d\n", choice);
	      }
	   }


	switch(choice)
	{
	    case 1:
	    	user_command = add_user(user_command);
	    	break;
	    case 2:
	    	user_command = change_type(user_command);
	    	break;
	    case 3:
	    	user_command = change_location(user_command);
	    	break;
	    case 4:
	    	user_command = remove_user(user_command);
	    	break;
	    default :
	    	printf("Unknown Command\n");
	}

	return user_command;
}

The add_user code for example, asks the user for information about the person they want to add to the system. Then the strings from the user input should be added together but separated by a "/", so it can be processed as a command later.

char* add_user(char* user_command)
{
	char staff_ID[80];
	char staff_name[80];
	char staff_type[80];
	char security_ID[80];

	printf("What is the StaffID of the staff member to be added: ");
	scanf("%s", staff_ID);

	printf("What is the name of the staff member to be added: ");
	scanf("%s", staff_name);

	printf("What is the type of the staff member to be added: ");
	scanf("%s", staff_type);

	printf("What is your StaffID: ");
	scanf("%s", security_ID);

	strcpy(user_command, "1");
	strcat(user_command, "/");

	strcat(user_command, staff_ID);
	strcat(user_command, "/");

	strcat(user_command, staff_name);
	strcat(user_command, "/");

	strcat(user_command, staff_type);
	strcat(user_command, "/");

	strcat(user_command, security_ID);

	printf("The full command is %s\n", user_command);


	return user_command;
}

But the string "user_command" appears to be empty. And the printf doesn't print...

Any ideas?

[tabstop]

Well, which printf doesn't print?

[FallenBlade]

"printf("The full command is %s\n", user_command);"

Sorry I should have made that clearer.

[tabstop]

Step 1: There had better be something in between the lines of code here:

char* user_command;

user_command = get_user_command(user_command);

where you actually create your string. Right now you have a pointer that could point to a string, if only you had one available for it to point to. Adding that actual creation seems to help:

$ ./str
-=Security Station=-
Add a User 	[1]
Change Type 	[2]
Change Location [3]
Remove User 	[4]
Choice: 1
number = 1
What is the StaffID of the staff member to be added: 2458
What is the name of the staff member to be added: tabstop
What is the type of the staff member to be added: E10
What is your StaffID: 1367
The full command is 1/2458/tabstop/E10/1367
1/2458/tabstop/E10/1367

[FallenBlade]

How would I do that, because I tried:

char* user_command;

	char temp[256];

	*user_command = temp;

	user_command = get_user_command(user_command);

And now it doesn't even ask me for the choice.

[tabstop]

Probably you should avoid syntax errors, is my guess:

user_command = temp;

[FallenBlade]

Sorry, quite new to C, and I'm not fully clued up on pointers.

Thanks a lot, fully functional now. Cheers.