reading a string into a structure

what iv'e done so far is read data from a dat file into a string, then validated it by checking there was enough data to fill the feilds in the struct then passed the string to a function.
here's where i fall over(doh!)
I need to read a string into a structure, so that i can run further validation test on 2 of the 4 members

switch(opt)
{
case 'I' :
case 'R' : f_num = sscanf(buff, "%1c %5s %6s %4d", &I_R_RECORD.rec_type,&I_R_RECORD.cust_code,
&I_R_RECORD.part_num, &I_R_RECORD.quantity);
if(f_num != 4)
error_rep(buff, error(5));
else
rpt(buff);

/*here iv'e check for the correct amount of records*/
/*and then passed the str to rpt();*/

void rpt(char *buff)
{

char code[6], part[7];
char *chk_digit, *chk_d;
FILE *fp;


while(fscanf(fp, "%[^\n]\n", buff) !=NULL)
{
while(fscanf(fp,"%1c%6s%7s%4d", &I_R_RECORD.rec_type,
&I_R_RECORD.cust_code,
&I_R_RECORD.part_num,
&I_R_RECORD.quantity) != '\n')
{
/*i know this doesn't work so any pionters on how to solve it*/
/*will be received with warm hands*/

chk_d_cust_num(code);
if(chk_digit)
strncat(I_R_RECORD.cust_code, chk_digit, 6);
else
error_rep(buff, error(1));
chk_d_part(part);
if(chk_d)
strncat(I_R_RECORD.part_num, chk_d, 7);
else
error_rep(buff, error(2));

}
}
fputs(buff, valid_rec_fp);
return;
}
Thanx in advs

You lost me

Why do you sscanf on buff, then attempt to overwrite it with
while(fscanf(fp, "%[^\n]\n", buff) !=NULL)

Oh, and fscanf returns neither NULL nor '\n' (at least not as you've written them).

Personally, I'd drop fscanf altogether, and just keep to reading the file using fgets, and decoding the line using sscanf

Code:

---

char buff[BUFSIZ];
while ( fgets( buff, sizof(buff), fp ) != NULL ) {
    // do stuff with buff
    // sscanf etc
}

---