Thread: Stream is reset but still getting bogus results.

all operations are on the file (stream). I am reading in the file, checking for one value, if found, report back, (reset stream) keep programming running. if not found report back ( reset stream) keep programming running.

there is no criteria to have an option to quit.
I added ftell to tell me what it is doing, it is showing 0 (zero) and still I get file not found when the information is valid. it is sporadic for the most part.
so I am not sure why it is not working all of the time.

Code:

#include <stdio.h>

int your_choice(void);
int item_number(void);


int main (int argc, const char **argv)
{
    
    if(argc < 2)
    {
        printf("no file\n");
        return -1;
    }
    
    FILE *fp;
    
    if ( (fp = fopen(argv[1], "r") ) == NULL )
    {
        printf("File < %s > no open, yo!\n", argv[1]);
        return -1;
    }
    
    char buffer[1024];
    int inputID = 0, flag = 0, ItemId = 0, quantity= 0, price = 0;  
    
    while (1)
    {
        your_choice();
        inputID = item_number();
            
        while (( fgets(buffer, sizeof buffer, fp)) != NULL)
        {
                //if found kick it back one
                //more loop and start over. 
                if ( flag == 1)
                {
                    fseek(fp,0,SEEK_SET);
                    printf("reset flag\ntell me %ld\n", ftell(fp) );
                    flag = 0;
                    break;
                }
            //run it through the entire file, or until a match
            //is found. 

//either way this loop is done same results are gotten

            //while ( sscanf(buffer, "%d", &ItemId) == 1 )
            while ( sscanf(buffer, "%d%d%d", &ItemId, &quantity, &price) == 3 )
            {
         
//used with other commented out while above
            //    sscanf(buffer, "%d%d%d", &ItemId, &quantity, &price);
                printf("running in inner loop\ntell me %ld\n", ftell(fp) );
                
                if ( inputID == ItemId )
                {
                    
                    printf("\n\n\nItemID Quantity Price Per Unit(SAR)\n");
                    printf("%d %10d %10d\n", ItemId,quantity,price);
                    getchar();
                    printf("\n\n\nPress Enter key to continue ...\n");
                    
                    //set stream back to start
                    fseek(fp,0,SEEK_SET);
                    
                    printf("inner loop\ntell me %ld\n", ftell(fp) );
                    
                    flag = 1;
                    getchar();
                    break;
                }        
            else
                {
                    //keeps it going until NULL, or EOF
                    break;
                }
            
         } //end inner loop    
         
          
     } //end outer loop
     //when buffer reaches NULL, to 
     //and to prevent it from chaning whenever
     // the it matchs, on break
    if ( inputID != ItemId)
    {
            getchar();
            //set stream back to start
            fseek(fp,0,SEEK_SET);
            printf("error not found\ntell me %ld\n", ftell(fp) );
            printf("\n\nError: Invalid item ID\n\n\n"
            "Press Enter key to continue ...\n");
            flag =1;
            getchar(); 
    }
        //set stream back to start
        //fseek(fp,0,SEEK_SET);
 }//end outer 3rd loop    
return 0;    
}


int your_choice(void)
{
    printf("Please Select your choice: ");
    
    int choice = 0;
    scanf(" %d", &choice);
    return choice;
}
    
int item_number(void)
{
    printf("Enter itemID: ");
    int item_number = 0;
    scanf(" %d", &item_number);
    return item_number;
}

test file

Code:

1000    3    10
1001    1    30
1002    6    23
1003    9    32
1004    42    55

some results

Code:

reset flag
tell me 0
Please Select your choise: 2
Enter itemID:     4222
running in inner loop
tell me 10
running in inner loop
tell me 20
running in inner loop
tell me 30
running in inner loop
tell me 40
running in inner loop
tell me 51
error not found
tell me 0


Error: Invalid item ID


Press Enter key to continue ...

Please Select your choise: 1
Enter itemID: 10004
reset flag
tell me 0
error not found
tell me 0


Error: Invalid item ID


Press Enter key to continue ...

Please Select your choise: 1
Enter itemID: 1004
reset flag
tell me 0

sscanf doesn't work the way you think. It doesn't use the buffer as a stream. It always reads from the start to the end, it doesn't remember where it was since the previous call of sscanf. To do what you want, you're better off using strtok.

EDIT: Actually, never mind, you use it correctly. I'm the one who misunderstood what the code is doing...

Originally Posted by GReaper

sscanf doesn't work the way you think. It doesn't use the buffer as a stream. It always reads from the start to the end, it doesn't remember where it was since the previous call of sscanf. To do what you want, you're better off using strtok.

EDIT: Actually, never mind, you use it correctly. I'm the one who misunderstood what the code is doing...

string token? Well at least it's good to know it wasn't strictly me per se' but that function.
thanks

edit fgets buffer is what is getting the "string" in the stream then sending it to sscanf, just thinking out loud.