basic file operations queries

This is a discussion on basic file operations queries within the C Programming forums, part of the General Programming Boards category; I'm C Programming learner. Please do clear my queries in detail. < My PC config : Linux with GNU GCC ...

  1. #1
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    Question 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..

  2. #2
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    Open the data file in notepad and paste it into code tags here... we need to see what's in it.

  3. #3
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    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.

  4. #4
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    Quote Originally Posted by mike65535 View Post
    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.

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    Quote Originally Posted by CommonTater View Post
    fscanf() should take care of the conversion for him...
    Ah, right.

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    Yes! Its working.. .

  7. #7
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    I mean, the pointer stream fp_file

  8. #8
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    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.

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