Reading dynamic length comma separated values using fscanf - c

Question

I have a txt file which contains patient details separated by commas
I want to read each value store that in a structure. But, the problem is that some of the entries contain 3 values and the others contain 4.
ENTRIES IN TXT FILE are:
1032,Pugsley Yanson,CELL,3048005191
1048,Banjo Codi,TBD,
1056,Lettuce Peas,WORK,7934346809
My Code looks like :
`struct Phone
{
char description[PHONE_DESC_LEN];
char number[PHONE_LEN];
};
// Data type: Patient
struct Patient
{
int patientNumber;
char name[NAME_LEN];
struct Phone phone;
};
void importPatients(const char* datafile, struct Patient patients[], int max){
FILE *fp = fopen(datafile, "r");
int i = 0;
int read = 0;
while (!feof(fp) && i < max){
read = fscanf(fp,"%d,%14[^,],%4[^,],%10[^,]\n",&patients[i].patientNumber,patients[i].name,patients[i].phone.description,patients[i].phone.number);
if(read == 0 && !feof(fp)){
fclose(fp);
return;
}
i++;
}
fclose(fp);
}
This code works perfectly when reading entries with 4 values but fails as soon as it encounters an entry with 3 values like: 1048,Banjo Codi,TBD,
How can this be fixed or is there a better approach to solve this problem?

Answer 1

At least these issues
Inconsistent ,
Sometimes a line of data ends with a final field, sometimes not.
1032,Pugsley Yanson,CELL,3048005191
1048,Banjo Codi,TBD,
Avoid line ending problems: read the line with fgets() and then parse.
Why is “while( !feof(file) )” always wrong?
Be sure char buffers are big enough
#define NAME_LEN (14 + 1)
#define PHONE_DESC_LEN ( 4 + 1)
#define PHONE_LEN (10 + 1)
Weak test
Do not test against 1 possible undesired return value. read could be other than 0 or 4. Test against desired return value.
// if(read == 0
if(read != 4
[Needs re-work, re-work done below]
Alternate:
char buf[100];
while (i < max && fgets(buf, sizeof buf, fp)){
int read = sscanf(buf,"%d , %14[^,], %4[^,], %10[^,]",
&patients[i].patientNumber, patients[i].name,
patients[i].phone.description, patients[i].phone.number);
if (read != 4) {
report_error();
} else {
i++;
}
}
fclose(fp);
[Update]
Untested sample code to better handle empty fields. Likely deserves more testing - later.
// Return patient count. -1 implies error
int importPatients(const char *datafile, struct Patient patients[], int max) {
FILE *fp = fopen(datafile, "r");
if (fp == NULL) {
return -1;
}
char buf[100];
int i = 0;
while (i < max && fgets(buf, sizeof buf, fp)) {
const char *token = strtok(buf, ',');
if (token == NULL) {
return -1;
}
patients[i].patientNumber = aoti(token); // Better code would use strtol()
token = strtok(buf, ',');
if (token == NULL) {
return -1;
}
snprintf(patients[i].name, sizeof patients[i].name, "%s", token); // TBD, check return value to buffer fit.
token = strtok(buf, ',');
if (token == NULL) {
return -1;
}
snprintf(patients[i].phone.description,
sizeof patients[i].phone.description, "%s", token);
token = strtok(buf, '\n');
if (token == NULL) {
return -1;
}
snprintf(patients[i].phone.number, sizeof patients[i].phone.number, "%s",
token);
i++;
}
fclose(fp);
return i;
}