Get string middle by C

Key:

void str_get_middlle( char *result, char *str, int start, int end ){

    int i;
    int c;

    for( str += start, i = 0; (start + i ) <= end && (*result++ = *str++) != ‘\0‘; i++ ){
                ;
    }

}

For example:

 1 #include <stdio.h>
 2 #include <stdlib.h>
 3 #include <string.h>
 4
 5 #define STR_LEN 10
 6
 7 void str_get_middlle( char *result, char *str, int start, int end );
 8
 9 int main( int argc, char *argv[] )
10 {
11     FILE *fp = NULL;
12     char *file_path = NULL;
13     char str[STR_LEN] = "", result[ STR_LEN ] = "";
14
15     if( argc == 1){
16         printf( "Too few augument(s)\n" );
17         exit( EXIT_FAILURE );
18     }
19
20     file_path = *(++argv);
21
22     if( (fp = fopen( file_path , "r" )) == NULL ){
23         printf( "Opening file error! path:%s\n", file_path );
24         exit( EXIT_FAILURE );
25     }
26     else{
27         printf( "Opening file [%s] was successfully!\n", file_path );
28     }
29
30
31     while( fgets( str, sizeof( str ),fp) != NULL ){
32 //        printf( "%s", str );
33         str_get_middlle( result, str, 0, 1);
34         printf( "%s-", result );
35
36         str_get_middlle( result, str, 2, 3);
37         printf( "%s-", result );
38
39         str_get_middlle( result, str, 4, 5);
40         printf( "%s\n", result );
41     }
42
43     return 0;
44 }

　　Means: 00112233 >> 00-11-22-33.　　This code can formt mac address.