Thread: How do you strip newline from char array?

I am reading in a txt file into an array - programData[100][6] from Main. I cannot change the element sizes per specs. Is the newline char even being saved since ALL words being read in are 5 characters long. Thus fgets() sees the newline from the txt file in the 6th position and appends a '\0' to the 6th position (over the newline) because the array size is only 6. So maybe I do not need to append my own '\0' char to the end since it would seem fgets() is doing that for me. So how to I get fptr to advance to the next line???? It seems that fgets is pausing on the first line on the second call and then advancing on the third call, this might be why counter when printed out shows 127 and then I get a seg fault since counter is integrated into fgets() and I've exceeed the array bounds. Any help appreciated. Thanks!!!

Code:

void readFileIntoArray(char programData[][6])
{
     
     FILE *fptr;
     int counter = 0;


     
     fptr = fopen("a:\\269data.txt","r");

     if (fptr == '\0')
     {
          printf("*****269data.txt file error - aborting program!*****\n");
          system("pause");
          exit(0);
     }
     
     if(feof(fptr))
     {
          printf("*****No data to read!*****\n");
          system("pause");
     }
 
     printf("\n\nTable 1 Initial Program Data as Read from 269data.txt...\n\n");
   
     while(!feof(fptr))     
     {
          fgets(programData[counter],6,fptr);
          programData[counter][6-1] = '\0'; //This doesn't work and I get a seg fault
          counter++; //counter seems to pass 100 and stops at 127 before crash                    
     }
         
}

> if (fptr == '\0')
Use == NULL

> while(!feof(fptr))
See the FAQ

> fgets(programData[counter],6,fptr);
The problem here is that if fgets() can't read the \n, then it's left for the next call.
So you're reading 5 characters on one call, then the \n on the next call - hence the alternating pattern you see.

Code:

char buff[BUFSIZ];
while ( counter < 100 && fgets( buff, sizeof buff, fptr ) != NULL ) {
  if ( strlen(buff) == 6 ) {
    /* 5 chars, and a newline*/
    strncpy( programData[counter], buff, 5 );
    programData[counter][5] = '\0';
    counter++;
  } else {
    /* report incorrect line */
  }
}

Originally Posted by pityocamptes

Thanks! As far as NULL vs '\0' our teacher said to use '\0' as NULL is not recognized by all compilers/platforms. Any truth to that? Thanks again.

I'm pretty sure NULL is standard C... or something. It should be defined but what is defined as is implementation specific.

> NULL is not recognized by all compilers/platforms. Any truth to that?
Maybe if your teacher has a fondness for some ancient pre-ANSI compiler.
It's part of ANSI-C, so there should be no excuse.

Besides, '\0' sends the wrong stylistic message as '\0' represents the nul character, not the NULL pointer. Using '\0' makes it seem like fgets() is returning a char!.

I suppose you could just use a bare 0 to represent a NULL pointer, which every C compiler should accept, and which is actually the definition of a NULL pointer in C++.

> fread(programData[index],6,1,fptr) != NULL
See, this is wrong as well - fread() returns the number of items read, not a pointer!
You were better off using fgets() to read a text file.

NULL is defined *somewhere* in the lib files... just think of it as doing

Code:

#define NULL (void*)0

Or something along those lines.


IMHO better programming practice would be to use

Code:

ptr = (type_name*)0;

instead of

Code:

ptr = 0;
ptr = NULL;

> IMHO better programming practice would be to use
IMO, it would not.
http://c-faq.com/null/nullptrmacro.html