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Scaninng from string

This is a discussion on Scaninng from string within the C Programming forums, part of the General Programming Boards category; i have the following function Code: void fixdate(char *pt, int* d, int* m, int* y, int* h, int* min, int* ...

  1. #1
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    Scaninng from string

    i have the following function

    Code:
    void fixdate(char *pt, int* d, int* m, int* y, int* h, int* min, int* pa)
    {
        char month[3];
        
        sscanf(pt, "%*s %d %s %d %d %d", d, month, y, h, min);
    
    
        if(*h>12)
        {
            *h = *h - 12;
            *pa = 2;
        }
        else
        {
            *pa = 1;
        }
    
    
        if(strcmp(month,"Jan") == 0)
        {
            *m = 1;
        }
        if(strcmp(month,"Feb") == 0)
        {
            *m = 2;
        }
        if(strcmp(month,"Mar") == 0)
        {
            *m = 3;
        }
        if(strcmp(month,"Apr") == 0)
        {
            *m = 4;
        }
        if(strcmp(month,"May") == 0)
        {
            *m = 5;
        }
        if(strcmp(month,"Jun") == 0)
        {
            *m = 6;
        }
        if(strcmp(month,"Jul") == 0)
        {
            *m = 7;
        }
        if(strcmp(month,"Aug") == 0)
        {
            *m = 8;
        }
        if(strcmp(month,"Sep") == 0)
        {
            *m = 9;
        }
        if(strcmp(month,"Oct") == 0)
        {
            *m = 10;
        }
        if(strcmp(month,"Nov") == 0)
        {
            *m = 11;
        }
        if(strcmp(month,"Dec") == 0)
        {
            *m = 12;
        }
    }
    i try to scan string with the following format sample

    Date: 25 Sep 2002 14:52:31

    when i check the values, the minute int equals 0. How can i properly scan the string taking in account the format of the string?

    i'm using sscanf(pt, "%*s %d %s %d %d %d", d, month, y, h, min);
    what should i change?
    Last edited by Donald Salguero; 10-24-2012 at 05:58 PM.

  2. #2
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    You're using an asterisk in the first format specifier to ignore the first string. Between 'h' and 'min', are there any special things you wish to ignore?

  3. #3
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    the complete string that i scan has the following format:
    "Date: dd month yyyy hh:mm:ss"

    the time is formatted as

    hh:mm:ss

    i want the hour int (*h) to be hh, and the minute int (*m) to be mm. I'm trying to ignore the colon in between hh and mm

    i'm using %*s to ignore "Date:" that is always at the begging of each string

  4. #4
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    You're using "%*s" to ignore a string. So what might you put to ignore a single character (such as ':')? And where?

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    i tried using
    sscanf(pt, "%*s %d %s %d %d %*[^:]c %d", d, month, y, h, min);
    sscanf(pt, "%*s %d %s %d %d %[^:]c %d", d, month, y, h, min);

    but the minute int always ended up as 0 even though the string shows different

  6. #6
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    Does it scan in the int variable "hours" correctly? Are you able to avoid scanning in the colons between the hours/minutes?

  7. #7
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    The only variable that causes me problems is the minute int. The hours are as they should be, and i can do the proper operations with them.

    If i had to guess is that after scanning the hours and while scanning the first colon the scan fails and stops, giving a null pointer to the minute pointer which would explain (i guess) why i get a 0 int when printing it.

  8. #8
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    I just ignore the g char.

    Code:
    #include <stdio.h>
    
    int main(void) {
       char s[]= {"Date: 25 Sep 2002 14:52:31"};
       char g;
       char month[4];
       int date,year,hour,minute,second;
       
       sscanf(s, "%*s %d %s %d %d%c%d%c%d",&date,month,&year,&hour,&g,&minute,&g,&second);
    
       printf("%d %s %d %d:%d:%d\n",date,month,year,hour,minute,second);
    
       printf("\n");
       return 0;
    }

  9. #9
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    thank you very much Adak, it worked as it should.

  10. #10
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    Service with a smile, mate.

  11. #11
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    If you need a specific character, just stick it into the scan pattern.

    Quote Originally Posted by Donald Salguero View Post
    i tried using
    sscanf(pt, "%*s %d %s %d %d %*[^:]c %d", d, month, y, h, min);
    That does not work, because the [ is the conversion specifier for character lists. "%*[^:]c" actually means "Skip (without storing) any number of non-colon characters. Then require a lowercase c in the input."

    The way I'd do this is
    Code:
    sscanf(pt, "%*s %d %3s %d %d:%d", d, month, y, h, min);
    which will return 5 if it successfully converted all five stored fields. (Skipped fields and pattern characters are not counted.) Also, it will simply return 2 instead of overflowing your month buffer if the date happens to be say "25 January 2012 23:59".

    Buffer overruns are bad, mmkay?

    Actually, you could make your month buffer longer (say nice round 16 characters total; using %15s in the pattern above), then simply do month[3] = '\0'; before the comparisons. That way you'd support both abbreviations and full month names.

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