Thread: Beginner Question: Problem with scanf and strings. Help!

First off how does scanf know that this: %[^\n] is supposed to be formatted for a String? Shouldn't %s need to be in there? According to the syntax it's not supposed to be.

Anyway, my real question is when I run this program (below) it lets me type in my first name, but then when I press Return it skips over letting me enter my last name and shows this:

Code:

What is your FIRST name: Bryan
What is your LAST name: Your FULL name is Bryan  and it is 6 long.

Code:

#include <stdio.h>
#include <string.h>

int main (int argc, const char * argv[]) {

	char		firstname[31];
	char		lastname[31];
	char		fullname[63];
	
	printf( "What is your FIRST name: " );
	scanf( "%[^\n]", firstname );      // accepts everything until it sees a \n
	
	printf( "What is your LAST name: " );
	scanf( "%[^\n]", lastname );      // accepts everything until it sees a \n
	
	strcpy( fullname, firstname );
	strcat( fullname, " " );
	strcat( fullname, lastname );
	
	printf( "Your FULL name is %s and it is %d long.", fullname, strlen(fullname) );
		  
    return 0;
}

I figured using a fflush(stdin); would clear the buffer but it doesn't seem to make a difference... I'm clueless how to get this working as expected

Code:

#include <stdio.h>
#include <string.h>

int main (int argc, const char * argv[]) {

	char		firstname[31];
	char		lastname[31];
	char		fullname[63];
	
	printf( "\nWhat is your FIRST name: " );
	scanf( "%[^\n]", firstname );
	fflush(stdin);                       // this doesn't seem to work
	
	printf( "\nWhat is your LAST name: " );
	scanf( "%[^\n]", lastname );
	
	strcpy( fullname, firstname );
	strcat( fullname, " " );
	strcat( fullname, lastname );
	
	printf( "\nYour FULL name is %s and is %d characters long.", fullname, strlen(fullname) );
		  
    return 0;
}

ohh ok... so it means ignore any characters after it sees the new line?

(in this code anyway)

I guess what's confusing me is I thought %[^\n] was to ignore the new line, but then %*c also ignores the new line. isn't that redundant?

if %[^\n] doesn't work by itself should I not use it?

Also is the * part of %*c acting as a "wildcard"? It's a bit confusing know what purpose it serves since it could be multiply (which wouldn't make any sense in this case) or referencing a pointer.

Originally Posted by MK27

No, it means ignore the newline, which is a single character ('\n'). So if you typed:

mk27\n

(the newline being because of the enter key), and you capture everything up to but not including the newline with %[^\n], '\n' is left in the buffer. %*c captures one more character and throws it away; because of the context, in this case that character would have to be the newline (get it?).

Originally Posted by lucidrave

I guess what's confusing me is I thought %[^\n] was to ignore the new line, but then %*c also ignores the new line. isn't that redundant?

As mentioned, %[^\n] means "get everything that isn't a newline". If you do that, well, the newline is still there since you got everything that wasn't a newline. You need to now do something with that newline, instead of what you seem to be doing which is "ignore it and hope that it goes away".