Thread: Better scanning method

Say I had a file with the following values in it

100 200 300 400 500

Now I want to assign a to 100, b to 300 and c to 500. Am I correct in thinking that fscanf has to scan through each one like this?

fscanf(file,"%d %d %d %d %d",&a,&b,&c,&d,&e);

There has to be a better way of doing that,without having the needless variables!!!

Here's the way:

Code:

# include <stdio.h>
# include <conio.h>

int main()
{
	FILE *fin= NULL;
	int Numbers = 0;

	fin = fopen("numbers.txt", "rt");

	while (fscanf(fin, "%d", &Numbers) != EOF)
	{
		printf("\nNumbers = %d", Numbers);
	}
	getch();
	return 0;
}

Have phun!

Originally posted by Sean
If that works, why don't you just use it? The whole idea of high level languages like C, is to not write code when someone else has done it for you.

...unless you can do it better, of course

What i'm basically trying to say is that I don't need 200 and 400 so why waste the space by declaring extra variables, especially when in some cases there can be 20+ values in a file and I only want to use 4 of those values for the program. Thanks GaPe but there doesn't seem to be a conio.h in linux

The "conio.h" library is just for the "getch()" command and it is used to stop the program. In this case it is useless.

So does that answer my problem then, taking the conio and getch out of your method just make the program print all the numbers.

Yes.

This methode is inefficient. If you want to save your numbers than you should do this with an array of integers.

besides, what does yours really do? if he wanted to store the numbers in an array of int, he could do something like this:

Code:

#include <stdio.h>
#include <stdlib.h> //for strtol()
#include <string.h> //for strlen()
#include <ctype.h> //for isdigit()

int main(void)
{
   char  line[1024]; 
   char *endp;
   int   iArray[100] = {NULL};
   int   i, j = 0;
   
   FILE *fileptr;
   
   if((fileptr = fopen("filename.txt", "r")) == NULL)
   {
      printf("Could not open file!\n");
      return 0;
   }

   
   while(fgets(line, sizeof(line), fileptr))
   {
      line[strlen(line) - 1] = '\0'; //removes the '\n'

      for(i = 0; i < strlen(line); ++i)
      {
         if(isdigit(line[i]))
         {
           iArray[j++] = strtol(&line[i], &endp, 10);
           while(isdigit(line[i])) ++i;
         }
      }
   }
   for(i = 0; i < j; ++i)
      printf("%d ", iArray[i]);   

   fclose(fileptr);
   getchar(); //not needed if run from command prompt
   return 0;
}

EDIT: bah, i should really compile these things first.
EDIT2: oops, didnt include 0 as a number that may show up in the file... not good... fixed now.

I was just showing him the way how to display the numbers. If you want to save them here's the way of doing it:

Code:

# include <stdio.h>
# include <conio.h>

int main()
{
	FILE *fin= NULL;
	int i = 0, Numbers = 0, IntArray[100];

	fin = fopen("numbers.txt", "rt");

	while (fscanf(fin, "%d", &Numbers) != EOF)
	{
		IntArray[i++] = Numbers;
	}
	getch();
	return 0;
}

Have phun!

you say you were showing him how to print out the numbers but his post wasnt asking for that.

I know that but I just want to show him how to read numbers from a file and I didn't want to give him a direct solution.

i still dont see how the efficiency of...

Code:

fscanf(file, "%d %*d %d %*d %d", &a, &b, &c);

really matters in this case. i just answered his question

And what about if you have 1000 of numbers in your file. What will you do?? Write 1000 variables for each number or you will be smart and saved them into an array of integers?