Thread: search a date

Hello,

I want to make a function (int search_date(FILE *fp,time_t time) that searches a date in a log file and makes the file pointer fp point to this date (if the date doesn't exist, point to the date immediately after the searched date ; if more than one date exists, point to the lattest one).
In my log, every line begins with a date, of the form "Dec 14 00:00:00".
Here is my program :

Code:

#include <stdio.h>
#include <string.h>
#include <time.h>
 
time_t string_to_time_t(char *s)
{
        time_t rawtime;
        struct tm * timeinfo;
        char month_s[4] ;
        int month,day,hour,minute,second;
        sscanf(s, "%3s %d %d:%d:%d", month_s, &day, &hour, &minute, &second);
 
        char * month_names[12]={"Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"};
        int i=0;
        while( strcmp(month_s,month_names[i]) != 0  )
                i++;
        month=i;
 
        time (&rawtime);
        timeinfo=localtime(&rawtime);
        timeinfo->tm_mon=month;
        timeinfo->tm_mday=day;
        timeinfo->tm_hour=hour;
        timeinfo->tm_min=minute;
        timeinfo->tm_sec=second;
        return mktime(timeinfo);
}
 
time_t get_date(FILE *fp)
{
        char s[16];
        return string_to_time_t(fgets(s,16,fp));
}
 
int goto_nextline(FILE *fp)
{
        int c; //EOF is a int
        do c=fgetc(fp) ;
        while ((c != '\n') &&  (c !=EOF));
        if (c=='\n')
                return 0;
        else
                return 1;
}
 
 
void goto_beginning_of_line(FILE *fp)
{
        int c;
        if (ftell(fp) !=0)
        {
                fseek(fp,1,SEEK_CUR);
                do
                {
                        fseek(fp,-2,SEEK_CUR);
                        c=fgetc(fp);
                }
                while ( ftell(fp)-2>=0 && c != '\n' );
                if( ftell(fp)==1 )
                        fseek(fp,-1,SEEK_CUR);
        }
}
 
int search_date(FILE *fp, time_t time)
{
        FILE *fpmin, *fpmax, *fptmp;
        time_t timemin, timemax;
        fpos_t pos;
        fpmin=fpmax=fptmp=fp;
        fseek(fpmin,0,SEEK_SET);
        fseek(fpmax,0,SEEK_END);
        fseek(fptmp,0,SEEK_SET);
        timemin=get_date(fpmin);
        goto_beginning_of_line(fpmax);
        timemax=get_date(fpmax);
        fgetpos(fpmin,&pos);
        while(goto_nextline(fpmin)==0 && get_date(fpmin)<time)
        {
                fsetpos(fpmin,&pos);
                fsetpos(fptmp,&pos);
                float weight=(float)(time-timemin)/(float)(timemax-timemin);
                long difference=ftell(fpmax)-ftell(fpmin);
                fseek(fptmp,(long) weight * difference,SEEK_CUR);
                goto_beginning_of_line(fptmp);
                if (time < get_date(fptmp))
                {
                        fpmax=fptmp;
                        timemax=get_date(fpmax);
                }
                else
                {
                        fpmin=fptmp;
                        timemin=get_date(fpmin);
                        fgetpos(fpmin,&pos);
                }
        }
        fp=fpmin;
        return 0;
}
 
int main(int argc, char **argv)
{
        FILE *fp=fopen("log.txt","r");
        if (fp==NULL)
                fprintf(stderr,"File can't be opened\n");
        else
        {
                time_t time=string_to_time_t("Dec 11 12:00:00");
                search_date(fp,time);
                //do some things here
        }
        fclose(fp);
        return 0;
}

This program doesn't work (segmentation fault).
Can you help me to make it work please?

Regards.

It says ./a.out : no such file or directory.

Ok it works now.
The answer is :
program received signal SIGSEGV, Segmentation fault.
0x0020c9ba in strcmp() from /lib/tls/i686/cmov/libc.so.6

the answer is No symbol i in current context

Well anyway it sounds clear to me why the strcmp is wrong : that's because the file pointer doesn't point to the beginning of a date (such as "Dec 12 00;00:00").
That's because there are some errors in search_date.
Can you help me to spot them and correct them please?