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Top Forums Programming Wildcard Pattern Matching In C Post 302976665 by Azrael on Sunday 3rd of July 2016 02:25:48 AM
Old 07-03-2016
Well, after no luck with fnmatch() and other pattern matching functions I found online I decided to give regex a try:

Code:
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <time.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <regex.h>

int main() {

   char newhold[40];

        regex_t re;
        time_t current = time(NULL);
        char day[10];
        char mon[10];
        int retval = 0;        

        strftime(day, sizeof(day), "%d", localtime(&current));
        strncat( newhold, day, 10 );
        strncat( newhold, "?", 2 );
        strftime(mon, sizeof(mon), "%b", localtime(&current));
        strncat( newhold, mon, 10 );
        strncat( newhold, "*", 2 );
        strncat( newhold, "pattern", 10 );

     if(regcomp(&re , newhold, REG_EXTENDED) != 0 ){
         return;
     }

    FILE *fp;
    fp = fopen("/var/log/apache2/other_vhosts_access.log", "r");
    char line[100];
    unsigned int i = 0;

    while(fgets(line, sizeof(line), fp)) {
        if ((retval = regexec(&re, line, 0, NULL, 0)) == 0){
        i++;
      }
    }
  printf("%s %d\n", newhold, i );
  fclose(fp);

  return 0;
}

Obviously this doesn't work. I know in the following part that "newhold" would normal have a constant defined instead of a char array. I could do that with the "pattern" section of this regex and with the "?" and "*" wildcards. However, the variables "day" and "mon" are going to be checked by the system every time the code runs. So a constant wouldn't work in this case.

Perhaps I'm going wrong in other aspects as well, but that's the biggest problem I see at the moment. Anyone know any tricks to pass variables into regex for this? I tried searching that online as well with no success. Maybe my Google-fu is just lacking?

Also I'm not finding much creating a file from the regcomp command either. I'd love to see that if anyone can provide an example.

Last edited by Azrael; 07-03-2016 at 05:05 AM..
 

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STRCAT(3)						     Linux Programmer's Manual							 STRCAT(3)

NAME
strcat, strncat - concatenate two strings SYNOPSIS
#include <string.h> char *strcat(char *dest, const char *src); char *strncat(char *dest, const char *src, size_t n); DESCRIPTION
The strcat() function appends the src string to the dest string, overwriting the null byte ('') at the end of dest, and then adds a ter- minating null byte. The strings may not overlap, and the dest string must have enough space for the result. The strncat() function is similar, except that * it will use at most n characters from src; and * src does not need to be null-terminated if it contains n or more characters. As with strcat(), the resulting string in dest is always null-terminated. If src contains n or more characters, strncat() writes n+1 characters to dest (n from src plus the terminating null byte). Therefore, the size of dest must be at least strlen(dest)+n+1. A simple implementation of strncat() might be: char* strncat(char *dest, const char *src, size_t n) { size_t dest_len = strlen(dest); size_t i; for (i = 0 ; i < n && src[i] != '' ; i++) dest[dest_len + i] = src[i]; dest[dest_len + i] = ''; return dest; } RETURN VALUE
The strcat() and strncat() functions return a pointer to the resulting string dest. CONFORMING TO
SVr4, 4.3BSD, C89, C99. SEE ALSO
bcopy(3), memccpy(3), memcpy(3), strcpy(3), string(3), strncpy(3), wcscat(3), wcsncat(3) COLOPHON
This page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. GNU
2010-09-20 STRCAT(3)
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