reading data file into string using string tokenizer - structure

Question

hi I have this code for reading text file into string
void addStu (BST_TREE* list)
{
// Local Declarations
COMPANY* stuPtr;
FILE* fp;
int i = 0;
char fileName[25];
char buffer [100];
char* tempString;
// Statements
stuPtr = (COMPANY*)malloc (sizeof (COMPANY));
stuPtr->name = (char*) malloc(128 * sizeof(char));
stuPtr->market = (char*) malloc(128 * sizeof(char));
stuPtr->initial = (char*) malloc(128 * sizeof(char));
tempString = (char*) malloc(128 * sizeof(char));
printf("Enter the file name: ");
gets(fileName);
fp = fopen(fileName, "r");
if(fp == NULL)
{
printf("Error cannot open the file!\n");
exit(101);
}
while(fgets(buffer, 100, fp) != NULL)
{
if (!stuPtr)
printf("MEmory overflow!\n"), exit(101);
tempString = buffer;
stuPtr->name = strtok(tempString, ";");
sscanf(buffer, "%15s %15s %f ", stuPtr->market, stuPtr->initial, &(stuPtr->stock));
BST_Insert(list, stuPtr);
i++;
} // end while
} //addStu
this code does not work properly since buffer keep on changing when i didn't even modify it
this is my input
Microsoft Corporation; NASDAQ MSFT 259.94B
Yahoo! Inc.; NASDAQ YHOO 37.67B
Baidu.com, Inc. (ADR); NASDAQ BIDU 8.64B
CNET Networks, Inc.; NASDAQ CNET 1.13B
QuickLogic Corporation; NASDAQ QUIK 88.62M
Answers Corporation; NASDAQ ANSW 53.49M
Apple Inc.; NASDAQ AAPL 114.17B
for example when I tried to read the first line, i was able to get stuPtr->name to contain Microsoft Coporation using string token, after this point the tempString would be modify to contain Microsoft Coporation as well, for some reason the buffer that was not suppose to change, changed as well leading to stuPtr->market, stuPtr->initial, and stuPtr->stock have the wrong input value.
why did buffer change without being modify? how can I fix this code to make it work ?
thank in advance for helping

Answer 1

strtok() has unexpected side-effect for OP.
After stuPtr->name = strtok(tempString, ";");, the buffer location formerly occupied by the ';' is replaced by a '\0'. So when sscanf(buffer, "%15s ... is called, unexpected results occur. Recommendation: consider alternatives other than mixing strtok() and 'sscanf()`.
One could continue on using sccanf() with
sscanf(&buffer[strlen(stuPtr->name)+1], "%15s ...
But recommend a sscanf() only solution or a strtok(), strtof().