Need help with segmentation fault

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C

Linux

debugging

This is my code, it can run. But when i run it it always says "There is segment fault". I run it on Ubuntu Linux. I don't know why it happens, if you know please tell me, thanks. :)

/*
   Copyright( c ), 2010, @ linux laboratory in xiyou.
   All rights reserved.

   File name: front_list.c.
   Programmer's name: Harry . wei.
   Start time: 5, 31.
   Finish time: 5,31.

   Programme's introduction: use front list to init the list.

   Modify time:
   Modify programmer:

   Modify introduction:

   */

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>

typedef	struct Mystruct_Node
{
	int	data;

	struct Mystruct_Node	* next;
}*Linklist, List;

int main( void )
{
	printf( "111111" );
	Linklist	l;
	Linklist	s;
	char 	c;
//	int	flag = 1;

	l -> next = NULL;

	printf( "Please enter characters:" );
	printf( "11111\n" );
	while( true )
	{
		c = getchar();

		if( c != '$' )
		{
			s = ( Linklist )malloc( sizeof( List ) );
			s -> data = c;
			s -> next = l -> next;               // First, s->next get the NULL value from l->next.
			l -> next = s;
		}
		else
		{
			break;
		}
	}

	l = l -> next;

	while( l -> next != NULL )
	{
		printf( "%c", l -> data );

		l = l -> next;
	}

	return( false );
	



}