How to get the number of lines in a file

This is a discussion on How to get the number of lines in a file within the C Programming forums, part of the General Programming Boards category; Hi all... How can I get the numer of lines in a file ? A solution is: char string[20 int ...

  1. #1
    Wanna-be :P delphi's Avatar
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    Unhappy How to get the number of lines in a file

    Hi all...

    How can I get the numer of lines in a file ?

    A solution is:

    char string[20
    int counter = 0;

    f = fopen ("blabla.txt", "r");

    while (fscanf(f, "%s", string)>0) counter++;


    But.. is there a better solution ? one which doesn't waste memory allocating a variable ?

    PS:

    while (fscanf(f, "%*s")>0) counter++; doesn't work


    PPS: I'm Using Borland C++ Builder

    Thx in advance

  2. #2
    ATH0 quzah's Avatar
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    Well first off, your answer wouldn't work right even if it did compile. All it does is count "words". If it didn't run off the end of the buffer and crash your program, it still wouldn't give the right answer.

    Read a character at a time. Test the character to see if it's the newline character. If it is, you've reached the end of a line. Repeat until you find the end of the file. While you're at it, go read the EOF FAQ.


    Quzah.
    Hope is the first step on the road to disappointment.

  3. #3
    Registered User mitakeet's Avatar
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    How about (untested):

    Code:
    while (!feof(fin)){
       if (fgetc(fin) == '\n') lineCount++;
    }

    Free code: http://sol-biotech.com/code/.

    It is not that old programmers are any smarter or code better, it is just that they have made the same stupid mistake so many times that it is second nature to fix it.
    --Me, I just made it up

    The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man.
    --George Bernard Shaw

  4. #4
    aoeuhtns
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    Then how about that line be
    Code:
    lineCount += (fgetc(fin) == '\n')

  5. #5
    ATH0 quzah's Avatar
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    Quote Originally Posted by mitakeet
    How about (untested):

    Code:
    while (!feof(fin)){
       if (fgetc(fin) == '\n') lineCount++;
    }
    How about reading the feof FAQ to see why your answer is wrong?


    Quzah.
    Hope is the first step on the road to disappointment.

  6. #6
    Wanna-be :P delphi's Avatar
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    Quote Originally Posted by quzah
    Well first off, your answer wouldn't work right even if it did compile.
    well.. yes.. i already know how my file is formatted (one string per line)... however it's better to code a general case, which will work for every case

    _________________________________________________
    Code:
    while (!feof(f)){
      counter += (fgetc(f) == '\n');
    }
    works... and obviously the mitakeet one too




    Thx a lot guys

    Cya
    Last edited by delphi; 07-14-2005 at 05:48 AM.

  7. #7
    ATH0 quzah's Avatar
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    Consider reading the FAQ on how to get a line from the user. You're not seeing the point here: %s stops at white space. A "string" in C is a series of characters terminated by a newline. By definition then, it could include spaces. You don't say if your file has spaces other than the newlines at the end of the file. If you do, then %s isn't going to read the whole line. Likewise, if any of your "strings" is longer than your array size (including room for the null), you can crash your program.

    At any rate, you may want to visit the FAQ anyway.


    Quzah.
    Hope is the first step on the road to disappointment.

  8. #8
    Wanna-be :P delphi's Avatar
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    well.. ok.. feof shouldn't be used.. then i can use this

    Code:
    char c;
    
    while ((c = fgetc(f))!=EOF){
    
       count += (c == '\n');
    
    }

  9. #9
    ATH0 quzah's Avatar
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    Nope. Some one didn't read the EOF FAQ like I suggested.

    On an aside, it'd likely be more efficient to test seperately from incrementing so you don't bother adding 0 over and over. Faster to check and if true increment, than to test and add for every character.


    Quzah.
    Hope is the first step on the road to disappointment.

  10. #10
    Wanna-be :P delphi's Avatar
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    Since i'm noob.. could u write the best code in your opinion :O

  11. #11
    Wanna-be :P delphi's Avatar
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    char c;

    Code:
    while ((c = fgetc(f))!=EOF){
    
       if (c=='\n')
       count++;
    
    }
    is it ok now ?

  12. #12
    ATH0 quzah's Avatar
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    Code:
    char c;
    Nope. Someone still didn't read the EOF FAQ.


    Quzah.
    Hope is the first step on the road to disappointment.

  13. #13
    Registered User mitakeet's Avatar
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    Quote Originally Posted by quzah
    How about reading the feof FAQ to see why your answer is wrong?


    Quzah.

    Care to explain to a dense 10 year professional programmer how my code is wrong? Your FAQ doesn't tell me how my code is flawed.

    Free code: http://sol-biotech.com/code/.

    It is not that old programmers are any smarter or code better, it is just that they have made the same stupid mistake so many times that it is second nature to fix it.
    --Me, I just made it up

    The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man.
    --George Bernard Shaw

  14. #14
    ATH0 quzah's Avatar
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    I guess a "10 year professional" can't read.


    Quzah.
    Hope is the first step on the road to disappointment.

  15. #15
    Registered User mitakeet's Avatar
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    Quote Originally Posted by quzah
    I guess a "10 year professional" can't read.


    Quzah.

    I have in fact read your FAQ and I see nothing that changes my mind. Care to point out where I am so wrong, you being so smart and all?

    Free code: http://sol-biotech.com/code/.

    It is not that old programmers are any smarter or code better, it is just that they have made the same stupid mistake so many times that it is second nature to fix it.
    --Me, I just made it up

    The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man.
    --George Bernard Shaw

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