C Beginner with files program problem!

This is a discussion on C Beginner with files program problem! within the C Programming forums, part of the General Programming Boards category; Beginner in C here, I can't seem to figure out what the problem here is. The display/search function goes into ...

  1. #1
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    Nov 2009
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    C Beginner with files program problem!

    Beginner in C here,
    I can't seem to figure out what the problem here is. The display/search function goes into an infinite loop and does not stop even after I specify break at end-of-file. Can someone please tell me what is wrong here.


    Code:
    void display(FILE *fp)
    {
     printf("USN  Name       Marks1 Marks2 Marks3\n");
     for(;;)
     {
    	fscanf(fp,"%d%s%d%d%d",&st.usn,st.name,&st.marks1,&st.marks2,&st.marks3);
    
    	if(feof(fp))                \\what is wrong here??!
    	 break;
    
    	printf("%-5d %-10s %-5d\t %-5d\t %-5d\n",st.usn,st.name,st.marks1,st.marks2,st.marks3);
      }
    }
    
    int search(FILE *fp,int key)
    {
        for(;;)
         {	fscanf(fp,"%d %s %d %d %d",&st.usn,&st.name,&st.marks1,&st.marks2,&st.marks3);
    
    	if(feof(fp))
    	 break;
    
    	if(key==st.usn)
    	return 1;
         }
        return(0);
    }

  2. #2
    cas
    cas is offline
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    Sep 2007
    Posts
    982
    If fscanf() encounters something it can't make sense of (say, a letter when it expected a number), it will stop reading. Thus end-of-file will never be triggered. Check the return value of fscanf(): it tells you how many successful conversions there were. If it's fewer than you expected, there will be some junk sitting around in the file just waiting to be (probably) ignored by fscanf() again, and so on ad infinitum.

    Of course I can't be certain this is the problem, but it's a good place to start looking.

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