NULL problem??

The below code is from my program. The variable 'input' is a line from a text file.

I'm trying to check if the line exists or not I am currently using NULL but it doesn't seem to work??

Am I correct using the NULL command or is there a specific command for checking whether that line exists within a text file??

Code:

if (input == NULL)

Thanks

You would be better served using int strcmp( string1, string2 ).
It returns 0 if the two strings are the same.

NULL is exactly the same as 0. It's not a command.

Write a function that takes a string as an argument and returns 1 if the string exists, 0 if it does not.

Inside the function, run a loop that tests each character with the isgraph() function. isgraph is found in ctype.h

Hope that helps!

Thanks that has helped but how do I check if a string exists or not?

Are you trying to check for a blank line? If so, maybe:

Code:

bool is_blank_line(char *input)
{
   int i;
   if (strlen(input) == 0)
      return 1;
   else
   {
      for (i=0; i<strlen(input); i++)
      {
         if (!isspace(input[i]))
            return 0;
      }
   }
   return 1;
}

//In your main() function:
#include <ctype.h>
.
.
   if (is_blank_line(input))
      cout << "line is blank.\n";
   else
      cout << "line is NOT blank.\n";