[c-prog] Need help sorting an array of structures

[~Rick]

All,

I have a structure defined below (I've eliminated some of the 
elements because it's big). It's setup to be part of a single linked 
list but at the moment I have an array built:

struct ENTRY    linedata[MAX_ENTS];

I am populating a number of entries and want to sort on the field 
linedata.transferPath. I'm using qsort and have built a comparator 
function but cannot figure out how to specify the transferPath 
element.  If I use a simple character array and try to sort on a 
column of that array, the following works (feel free to optimize it):

int comparePath (const void * a, const void * b)
{
     char *a1    = (char *)a;
     char *b1    = (char *)b;
     char *a2    = &a1[TRANSTAB-1];
     char *b2    = &b1[TRANSTAB-1];

     return (strcmp((char *)a2, (char *)b2));
}

But, I want to sort on an element within a structure. I've tried, and 
it fails. How can I specify the element to the comparator? (Darn 
pointers!)? I haven't worked with qsort or comparator functions before.

int compareEntry (const void * a, const void * b)
{
     char *a1    = (char *)a;
     char *b1    = (char *)b;
     char *a2    = a1.transferPath;
     char *b2    = b1.transferPath;

     return (strcmp((char *)a2, (char *)b2));
}


struct ENTRY {
     struct ENTRY *next;
     long int     ruleCnt;
     char         ruleKey[5];
     char         *ruleKeyword;
     char         *ruleValue;
     int          labelCnt;
     char         labelKey[6];
     char         labelValue[2];
     int          junkCnt;
     char         junkKey[5];
     int          transferCnt;
     char         transferKey[9];
     char         *transferPath;
     int          header1Cnt;
     char         header1Key[8];
     char         *header1Value;
     int          verb1Cnt;
     char         verb1Key[5];
     char         *verb1Value;
     int          value1Cnt;
     char         value1Key[6];
     char         *value1Value;
     int          conjunctionCnt;
     char         conjunctionKey[12];
     char         *conjunctionValue;
     int          header2Cnt;
     char         header2Key[8];
     char         *header2Value;
     int          verb2Cnt;
     char         verb2Key[5];
     char         *verb2Value;
     int          value2Cnt;
     char         value2Key[6];
     char         *value2Value;
     char         *data;
};