matching the newline

This is a discussion on matching the newline within the C Programming forums, part of the General Programming Boards category; hi all, i'm so mess up with this problem. suppose a data file Data.dat: 0 1 3 4 1 3 ...

  1. #1
    taj
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    matching the newline

    hi all, i'm so mess up with this problem.
    suppose a data file Data.dat:

    0 1 3 4
    1 3
    2 4

    how can i stop read those numbers when matching the newline?
    PS: # of numbers must be counted.


    Thanks

  2. #2
    taj
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    This my code

    Code:
      int main()
    
    {
      
      int i,j;
      int z[500];
      FILE *num_cluster=NULL;
      num_cluster = fopen("clus_size.dat","r");
         i=0;
         while(fscanf(num_cluster, "%d", &z[500])!=EOF)
        {
              printf("%d\n", z[500]);
              if(z[500]=='\n'){
                break;
                printf("newline matched, stop reading file!\n");
               }
               i++;
         }
      
         fclose(num_cluster);
        return 0;
    }

  3. #3
    Registered User mitakeet's Avatar
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    All wrong. RTFM scanf before you go much further!

    Try this (compiled, but not tested):

    Code:
    #include <stdio.h>
    #include <stdlib.h>
    
    int main() {
        int i,j;
        int z[500];
        FILE *num_cluster=NULL;
        num_cluster = fopen("clus_size.dat","r");
        if (!num_cluster){
            fprintf(stderr, "Can't open input file!\n");
            exit(1);
        }
    
        i=0;
        while(fscanf(num_cluster, "%d", &z[i]) == 1) {
            printf("%d\n", z[i]);
            i++;
            if (i>=500){
                fprintf(stderr, "Too many numbers!\n");
                break;
            }
        }
    
        fclose(num_cluster);
        return 0;
    }
    This won't help you read in one line's worth at a time, you will have to do your own buffering for that.

    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
    Registered User mitakeet's Avatar
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    This will do what you want, though it is quite sensitive to the format of your input file (it basically requires that there be a linefeed immediately after the last number):

    Code:
    #include <stdio.h>
    #include <stdlib.h>
    
    int main() {
        int i,j, chr;
        int z[500];
        char buf[40];
        FILE *num_cluster=NULL;
        num_cluster = fopen("clus_size.dat","r");
        if (!num_cluster){
            fprintf(stderr, "Can't open input file!\n");
            exit(1);
        }
    
        i=0;
        while(fscanf(num_cluster, "%39s", buf) == 1) {
            z[i] = atoi(buf);
            printf("%d ", z[i]);
            if ((chr = getc(num_cluster)) == '\n'){
                printf("We found a linefeed!\n");
            }else{
                ungetc(chr, num_cluster);
            }
            i++;
            if (i>=500){
                fprintf(stderr, "Too many numbers!\n");
                break;
            }
        }
    
        fclose(num_cluster);
        return 0;
    }

    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

  5. #5
    taj
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    Thanks for that , I forgot to say that i am not good in C programming , I just start to do so , so please help me !!!

  6. #6
    taj
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    Thaks mitakeet , But it doesn't work !!!

  7. #7
    Just Lurking Dave_Sinkula's Avatar
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    If you're just going to read the first line, then consider reading it into a string using fgets. Then you can parse the string into individual values.
    Code:
    #include <stdio.h>
    
    int main()
    {
       FILE *file = fopen("file.txt","r");
       if ( file != NULL )
       {
          char line[BUFSIZ];
          /*
           * Read the line of text.
           */
          if ( fgets(line, sizeof line, file) != NULL )
          {
             int i = 0, j, n, z[500];
             char *ptr = line;
             fclose(file);
             /*
              * Parse the numbers from the string.
              */
             while ( sscanf(ptr, "%d%n", &z[i], &n) == 1 )
             {
                ptr += n;
                ++i;
             }
             /*
              * Output the data.
              */
             for ( j = 0; j < i; ++j )
             {
                printf("z[%d] = %d\n", j, z[j]);
             }
          }
       }
       return 0;
    }
    
    /* file.txt
    0 1 3 4
    1 3
    2 4
    */
    
    /* my output
    z[0] = 0
    z[1] = 1
    z[2] = 3
    z[3] = 4
    */
    7. It is easier to write an incorrect program than understand a correct one.
    40. There are two ways to write error-free programs; only the third one works.*

  8. #8
    taj
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    Thanks Dave_Sinkula , But I would like the out put will be same as the data file !!! any help

  9. #9
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    First, a disclaimer---I don't use C style I/O very much so take everything here with a grain of salt, look it up yourself, and/or verify my ideas before trying them out yourselr.

    Second, I assume a line is defined as a string ending with a newline char as opposed to line on the screen, etc.

    Given that, when I looked it up fscanf(), it appears to stop input into a string at whitespaces. Therefore, I doubt that fscanf() will differentiate between spaces, newline char, tabs, etc, as the terminating char. So how could you tell when you reached the end of a line to stop counting the number of ints on the line?

    fgetc() apparently reads one char at a time. Therefore the input could be assessed char by char, with the number of ints being counted until a newline char is found. However, what happens if the int in the file has more than one digit?

    fgets() apparently reads up to a specified number of char into the given string or until a newline or EOF is encountered. Therefore, you could read a whole line at a time into a string at a time. Once you have isolated a string of chars representing a given line you could then count the number of white spaces in the string and add 1 to get a rough idea of the number of ints or get a better count by parsing the original string into substrings using strtok() and counting the number of substrings isolated, or parsing the original string into substrings using sscanf() and counting the number of substrings identified, or whatever other technique you want to try.
    You're only born perfect.

  10. #10
    Registered User mitakeet's Avatar
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    The problem with fgets() (and why I didn't use it) is that if you have lines longer than your buffer you get truncation with the next read being the remainder of the buffer (presuming it is still large enough). That means you have to have complex code to detect when you have more data remaining and have to stitch together the remaining bits from the previous read. If you can use C++ use the string class and the version of getline in <string> and then parse with a stringstream.

    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

  11. #11
    Just Lurking Dave_Sinkula's Avatar
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    Quote Originally Posted by mitakeet
    The problem with fgets() (and why I didn't use it) is that if you have lines longer than your buffer you get truncation with the next read being the remainder of the buffer (presuming it is still large enough).
    Well, there is a similar issue with the size of the string to contain the text representation of the integer value. That one is just buried deeper. Such a thing could be portablized, but that is a bit icky.

    [edit]Although the 40-char buffer would be good enough for a 126-bit integer, so it would be a safe assumption for quite some time one would think.
    Last edited by Dave_Sinkula; 07-14-2005 at 01:53 PM.
    7. It is easier to write an incorrect program than understand a correct one.
    40. There are two ways to write error-free programs; only the third one works.*

  12. #12
    taj
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    Thanks alot Dave_Sinkula , it works , and as what i need , agian thanks alot

  13. #13
    ATH0 quzah's Avatar
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    Well since we're all having fun here, here's a variation of a theme...
    Code:
    int c, l = 0, x=0, array[ BUFSIZ ] = {0};
    while ( (c = fgetc( fp )) != EOF && c != '\n' )
    {
        if ( isdigit( c ) )
        {
            if ( isdigit( l ) )
                array[ x ] *= 10;
            array[ x ] += c - '0';
        }
        else
        if( isdigit( l ) )
            x++;
        l = c;
    }
    I think that'll do the trick.

    [edit] I think that fixes an indexing bug where the last character wasn't a digit so it incremented too much. Haven't tested that last change. [/edit]

    Quzah.
    Last edited by quzah; 07-14-2005 at 01:10 PM.
    Hope is the first step on the road to disappointment.

  14. #14
    taj
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    Hi quzah

    Please could you explain to me , i didn't understand what you did , I am not very good in C

  15. #15
    ATH0 quzah's Avatar
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    I read the file one character at a time, and if it's not the end of file marker (EOF) or a newline, I process that character. We use the following:

    a) If it is a digit (0 - 9), we use the current array spot for it. First, we multiply what's there by 10, and then add this character's decimal value. This allows us to read numbers that are bigger than one digit correctly. (At least until you overflow your integer, but that's a different issue...)
    b) If it's not a digit, but the last character we read was a digit, we have to advance our array's index.
    c) Finally, we copy this character to the "last character" place holder so we can use it for future reference (as we do in step b).


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

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