Thread: how to detect end of line

Hi. I'm reading integers from a file and placing them into an array.
How do you detect for end-of-line? I've tried checking using '\0' and '\n', neither works.
If I can detect the end-of-line then I can remove the 0 that adds itself to the array.

Code:

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <math.h>

int main()
{
   /*Initialisations*/
   FILE *fin;
   char file_name_in[20]= "test.txt",c;
   long int int_array[10000],temp_array[1000],d,j=0,k=0,temp_integer=0,size_of_array=0;

   /* Test to see if file opens */
   fin = fopen(file_name_in, "r");
   if (fin == NULL){
      (void)fprintf(stderr,"Cannot open input file %s\n",file_name_in);
   }

   int i=0;
   do{
      c = getc(fin);
      if (((c == ' ')||(c == '\0'))&&(i!=0)){
         temp_integer = 0;
         for (j=0;i>0;j++){
            i-=1;
            temp_integer += (pow(10,i))*temp_array[j];
         }
         int_array[k] = temp_integer;
         printf("\nint_array at position %d is %d\n",k,int_array[k]);
         k++;
      }
      d = atoi(&c);
      temp_array[i]= d;
      i++;
   }while (c!=EOF);

   return 0;
}

sample input data:
2 300
4 800
10 10
10 10
10 10
10 100
10 10

The output:
int_array at position 0 is 2

int_array at position 1 is 30004

int_array at position 2 is 800010

int_array at position 3 is 10010

int_array at position 4 is 10010

int_array at position 5 is 10010

int_array at position 6 is 100010

Any Ideas?

You can check a string whether it contains an end-of-line sequence by testing for the character '\n', of course, but there isn't a function to tell you that the current file position is "at the end of a line".
If you have a line-based file format, it's sometimes easiest to use two levels of parsing. First, read in a whole line using the global std::getline function. Then use an std::istringstream to parse that as necessary. Repeat for each line in the input file.
You should generally never need to ever use eof() directly, of course. Just keep reading lines until the stream evaluates to false in a boolean context.
Forexample:

Code:

std::ifstream input("input.dat");
std::string line;
// For each line...
while (std::getline(input, line)) {    
                                       std::istringstream iss(line);
                                       char c;
    // For each character token...    
                                                 while (iss >> c) {      
  // Do something with c                                      }
                                                  }

Originally Posted by a_satari

Hi. I'm reading integers from a file and placing them into an array.

Are they integers or are they ascii characters? From your code I get that you are reading a string from a file. I don't get what you are doing in the if clause in the do/while loop, it seems like you would want to advance the file pointer there. But you are probably better of using fgets().

I don't think if fgets() will work as it just reads the whole file till the end of file marker or just allows to input a single string till the '/n'....

I didn't check but logically it seems to be like this.....

Well, you can wrap the fgets call inside a while loop condition, then do the conversion inside the loop body. fgets() does what getline does.

Originally Posted by Mr.777

Forexample:

Code:

std::ifstream input("input.dat");
std::string line;

Not in C you won't.... That's C++ code.

Originally Posted by CommonTater

Not in C you won't.... That's C++ code.

Yup... Sorry... My bad ;-)

what I'm really trying to ask is, how do you determine end of line?
In my outputs, the end of line is represented as a 0.
I want to get rid of this. So far I've used if statements to check for the following :
'/n'
'/0'
NULL
0x20 - which I think is ascii for end of line.

none of which have worked.

Thanks itsme86. I don't completely understand how 0 marks the end of line either.
I think it may be to do with reading the character using getc then converting it to an int using
atoi.
I'm going to try a few thing using getw which I'm told reads integers.

I think itsme86 was suggesting that 0 doesn't actually mark the end of your lines. The end of a line is marked with '\n'. The end of a string is marked with '\0'. As for getc, it already returns an int (not a char, see: Question 12.1). Trying to use atoi on the result will likely give you a seg fault, since atoi expects a char pointer. getw is most likely not what you want. It is for reading a binary word, not a text word.