Loop problem...Is is possible to delete a line of printed text??

This is a discussion on Loop problem...Is is possible to delete a line of printed text?? within the C Programming forums, part of the General Programming Boards category; I wrote a program that reads in a file into an array of structures. I am supposed to check that ...

  1. #1
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    Loop problem...Is is possible to delete a line of printed text??

    I wrote a program that reads in a file into an array of structures. I am supposed to check that the data is valid while reading it in. It should read in 7 elements into the structure and print an Invalid Data message if anything besides 7 elements are read in correctly. The program has a loop that should break when the end of the file is reached but for some reason it still loops one more time and therefore prints a false Invalid Data statement. I can't figure out the logic to change my loop so this will not happen. Crazy idea but can i just somehow delete that last Invalid Data statement somehow??? Or how can I change the loop?

    Here is the code
    Code:
    //open file
    fp = fopen(argv[1], "r");  
    if (fp == NULL)
      {
      printf("Error: Could not open file for read.\n\n");
      return EXIT_FAILURE;
      } //if
    
    //now open and take care of fscanf with : between fields
    while ((fgets(buffer, 1000, fp) != NULL) && i < 100)
            {
              result = sscanf(buffer, "%20[A-za-z ,]:%6[0-9]:%d:%d:%d:%d:%s", stuAry[i].name, stuAry[i].studentID, &stuAry[i].scoreOne, &stuAry[i].scoreTwo, &stuAry[i].scoreThree, &stuAry[i].scoreFour,
    stuAry[i].grade);
     
     
              if (result == EOF)
              {
               break;
                    } /* close if */
     
                    else if (result != 7)
                            {
                              printf("Invalid Record: %s", buffer);  
                                    } /* close second if */else if (result == 7)
                              {
                                    sum = (stuAry[i].scoreOne + stuAry[i].scoreTwo + stuAry[i].scoreThree + stuAry[i].scoreFour);
                                    stuAry[i].average = (sum / 4);
                                    i++;
                                } //if
             } //while
    and when I run the program I get this

    Code:
    Invalid Record: Data, Bad:9876543:100:34:54:21:F
    Invalid Record: Data, Missing:123456:100::99:50:C
    Invalid Record:
    How can I get rid of that last line?

    Thanks

  2. #2
    and the Hat of Guessing tabstop's Avatar
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    Are you sure there's not a blank line in your input? You appear to be doing the file handling correctly.

  3. #3
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    Your current problem can be fixed by checking your result returned from sscanf(), and when the result is < 2, break.

    That will stop the newline at the end of the file, from causing a misprint.

    This is an error you are not troubled with, yet:

    Code:
    sscanf("&#37;[A-za-z ,] etc.
    
    
    //should be:
    
    sscanf("%[A-Za-z ,] etc.

  4. #4
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    alright thanks guys

    And Adak thanks nice catch

  5. #5
    Kernel hacker
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    And to emphasize what Adak says: sscanf() is most likely NEVER going to return EOF.

    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  6. #6
    Frequently Quite Prolix dwks's Avatar
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    Also, your code might be a little more maintainable and easier to read if you processed each number on a line in a loop, with something like this.
    Code:
    char buffer[BUFSIZ];
    // read buffer
    char *start = buffer;
    int add;  // how much data was processed
    int number, sum = 0;
    
    while(sscanf(start, "&#37;d%n", number, &add) == 2) {
        sum += number;
        start += add;
    }
    
    // now sum is the sum of all of the numbers
    Just a thought. What you have works fine too.
    dwk

    Seek and ye shall find. quaere et invenies.

    "Simplicity does not precede complexity, but follows it." -- Alan Perlis
    "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
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  7. #7
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    Code:
    while(sscanf(start, "%d%n", &number, &add) == 2) {
    ?

    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  8. #8
    CSharpener vart's Avatar
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    Quote Originally Posted by matsp View Post
    Code:
    while(sscanf(start, "%d%n", &number, &add) == 2) {
    ?

    --
    Mats
    I'm not sure %n is counted by scanf...

    At least in the VS6 - it does not :

    Code:
    #include <stdio.h>
    
    int main(void)
    {
    	int n,k;
    	int m = sscanf("100 200","%d%n", &n,&k);
    	printf("m=%d k=%d\n", m,k);
    	return 0;
    }
    Output:
    Code:
    m=1 k=3
    Press any key to continue
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  9. #9
    Frequently Quite Prolix dwks's Avatar
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    From a man page:
    The C standard
    says: `Execution of a &#37;n directive does not incre-
    ment the assignment count returned at the comple-
    tion of execution' but the Corrigendum seems to
    contradict this. Probably it is wise not to make
    any assumptions on the effect of %n conversions on
    the return value.
    So it would probably be best to use "%d%n" and make sure the return value is >= 1.

    Yeah, and I made a mistake in omitting that ampersand.

    Anyway, strtol() is much easier to use in this case in my opinion anyway.
    dwk

    Seek and ye shall find. quaere et invenies.

    "Simplicity does not precede complexity, but follows it." -- Alan Perlis
    "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
    "The only real mistake is the one from which we learn nothing." -- John Powell


    Other boards: DaniWeb, TPS
    Unofficial Wiki FAQ: cpwiki.sf.net

    My website: http://dwks.theprogrammingsite.com/
    Projects: codeform, xuni, atlantis, nort, etc.

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