Question

I am just tokenizing a sentence and putting it onto a stack and then popping each token back off and printing the contents. Everything works the way it should except I am getting a blank line after it prints the first token. It only seems to do this when I am printing a %s if I use anything else the information is garbage but I dont get a blank line. I already tried a small function to ensure that strips out the newline character that fgets grabs. Any help is appreciated.

#define BUFFER_SIZE 100
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

// self-referential structure
struct stackNode
{   
   char *cData;
   struct stackNode *pNext;
};

typedef struct stackNode StackNode;
typedef StackNode *StackNodePtr;

// function prototypes
void push( StackNodePtr *pTop, char *cInfo );
char* pop( StackNodePtr *pTop );
int isEmpty( StackNodePtr pTop );
void printStack( StackNodePtr pCurrent );


int main(void)
{
    char sInput[BUFFER_SIZE];
    StackNodePtr pStack = NULL;
    char *pToken = NULL;
    int iIndex;

    printf("Please enter a word to be tokenized\n");

    fgets(sInput, BUFFER_SIZE, stdin);

    pToken = strtok(sInput, ", ");

    while(pToken != NULL)
    {
        push(&pStack, pToken);
        pToken = strtok(NULL, " ,");
    }

    while (isEmpty(pStack) == 0)
    {
        printf("%s\n", pop(&pStack));
    }
    return 0;
}

// Insert a node at the stack top
void push( StackNodePtr *pTop, char *cInfo )
{ 
   StackNodePtr pNew;

   pNew = malloc( sizeof( StackNode ) );

   if ( pNew != NULL )
   {   
      pNew->cData = cInfo;
      pNew->pNext = *pTop; // insert at top of stack
      *pTop = pNew;
   }
   else
   {
      printf( "%d not inserted. No memory available.\n", cInfo );
   }
} 

// Remove a node from the stack top
char* pop( StackNodePtr *pTop )
{ 
   StackNodePtr pTemp;
   char *cPopValue;

   pTemp = *pTop; // attach a pointer to element to be removed
   cPopValue = ( *pTop )->cData; 
   *pTop = ( *pTop )->pNext; // remove at top of stack
   free( pTemp ); // release this memory and set it free!

   return cPopValue;
}

int isEmpty( StackNodePtr pTop )
{ 
   return pTop == NULL;
} 

Answer 1

When you use fgets, you read a line including the '\n' in the end. when you tokenize the string, this '\n' is in the last token. when you print this token, you print the '\n' too. You should remove it by hand, or use scanf.

EDIT: from man fgets:

Reading stops after an EOF or a newline.
If a newline is read, it is stored into the  buffer.