Thread: basic file operations queries

I'm C Programming learner.
Please do clear my queries in detail.
< My PC config : Linux with GNU GCC compiler >

1) How to take a file as input which contains integers and display on screen.
I used the following code but its not working :

Code:

# include <stdio.h>
int main ( int argc, int *argv[1] )
{
FILE *fp_file;
int num;

fp_file = fopen ( argv[1], "r" );
fscanf  (fp_file,"%d",&num);
fprintf  (stdout,"%d",num);

fclose (fp_file);
return ;
}

This is what I used and I'm getting errors. Instead If I replace 'int' by 'char' @ argv[] , @ num and replace %d by %c, its working..
but here the issue is that I'm getting only the first letter of the characters in the file on the screen. Even though I didn't give any white spaces.
I then replaced fscanf() and fprintf() functions with fputc and fgetc but the output is same.

how do I make sure that a) I get the whole characters without using arrays concept. b) how do I get numbers on my screen.
c) can't I use int type in declaring arguments in main function.

2) I want to take input a file which contain some number and my program should read and take that number into a declared variable. how to do it.

* also please give me tips how troubleshoot myself..

Open the data file in notepad and paste it into code tags here... we need to see what's in it.

Well, remember that although the data *looks* like integers, they are really characters (it's an ASCII file, right?)

You should always test fp_file to see if fopen worked.

Originally Posted by mike65535

Well, remember that although the data *looks* like integers, they are really characters (it's an ASCII file, right?)

That's why I want to see the file... fscanf() should take care of the conversion for him...

You should always test fp_file to see if fopen worked.

Yep... and he should test the return value of fscanf() to make sure the conversion worked before printing.

Originally Posted by CommonTater

fscanf() should take care of the conversion for him...

Ah, right.

Yes! Its working.. .

I mean, the pointer stream fp_file

also please give me tips how troubleshoot myself..

Best advice I can offer is to write a little code, test a lot. This means you generate compartmentalized code, a piece at a time. You'll never code yourself into a corner if you test along the way.