Strange problem

This is a discussion on Strange problem within the C Programming forums, part of the General Programming Boards category; Hi, Could anyone please explain this problem to me? I use: Code: while(!feof(f)) { fgets (all_id, 100 , f); sscanf ...

  1. #1
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    Strange problem

    Hi,

    Could anyone please explain this problem to me?
    I use:
    Code:
    
    while(!feof(f))
    		  {
    			fgets (all_id, 100 , f);
    			sscanf (all_id,"%*s %s %s",a_id,d_id);
    			str[i] = a_id;
                            printf("\n%s",str[i]);
    			strtok(a_id,"G");
    			ida = strtok (NULL, "G");
    			idsa[i]=atoi(ida);
    			
    			i++;
    			
    		  }
    
    printf("\n%s",str[2]);
    Even if I use strncpy in place of strtok, the value retained by the str is the last value assigned to it using str[i]=a_id!
    Why cannot the str retain its value outside loop?
    I'll be obliged if anyone could explain this fundamental misconception of mine?

    Thanks,
    Angkar

  2. #2
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    Precisely I see its a stale value! When I switch back to strtok again, its throwing the value of the last result that I got using strncpy!!!

  3. #3
    Registered User 00Sven's Avatar
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    Try changing the loop to something other than feof. Why it's bad to use feof() to control a loop It can cause some wierd things about how many times the loop runs. Fix that, it might help.
    ~Sven
    Windows XP Home Edition - Dev-C++ 4.9.9.2
    Quote Originally Posted by "The C Programming Language" by Brian W. Kernignhan and Dennis M. Ritchie
    int fflush(FILE *stream)
    On an output stream, fflush causes any buffered but unwritten data to be written; On an input stream, the effect is undefined. It returns EOF for a write error, and zero otherwise. fflush(NULL) flushes all output streams.
    board.theprogrammingsite.com

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    What are the alternatives?

  5. #5
    and the hat of wrongness Salem's Avatar
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    > What are the alternatives?
    Sticking to one thread and not spamming the board would help.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
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