CODEWITHSUNDEEP
c
Ryanv048
Ryanv048

Reputation: 41

Can't figure out why my print statement keeps printing out twice

hey guys so I have this code i'm working with and it's doing everything i need it to do, however, i can't figure out why my printf is printing out twice for level. here is the code.

while(fgets(str_read, sizeof(str_read)-1 , fptr)!= NULL)
    sscanf(str_read, "%d ", &somearray->level);
    printf("level: %d\n", somearray->level);

also if there is anything else i could work on im open to feed back. i'm working with a .txt file that has the following setup:

int
name
int
name
int
name

Upvotes: 2

Views: 127

Answers (2)

Tom Karzes
Tom Karzes

Reputation: 24052

You need to check the return value from sscanf. On lines that don't contain an integer, it will return 0. In that case, somearray->level will be unchanged, so you'll print it a second time.

One possible solution is:

while(fgets(str_read, sizeof(str_read)-1 , fptr)!= NULL)
    if (sscanf(str_read, "%d ", &somearray->level) == 1)
        printf("level: %d\n", somearray->level);

This attempts the sscanf for every line, but only prints the result if a value was found.

Another solution would be to keep track of even vs. odd lines, and only attempt the sscanf on odd lines.

Upvotes: 1

paxdiablo
paxdiablo

Reputation: 881453

First off, I'm going to assume your code has braces around it since otherwise, it would only print once at the end (braces control what's in a loop body, not indentation):

while(fgets(str_read, sizeof(str_read)-1 , fptr)!= NULL) {
    sscanf(str_read, "%d ", &somearray->level);
    printf("level: %d\n", somearray->level);
}

That gels with what you're seeing. If your text file consists of alternating integers and non-integer names, every second sscanf will fail because a name cannot be treated as an integer. Since you don't check the return value, you just blindly assume the conversion worked and print the value that was previously in somearray->level.

Calls to the scanf family of function should generally include a check to ensure everything was correctly scanned, something like:

if (sscanf(str_read, "%d ", &somearray->level) != 1) {
    handleBadScan();
}

Upvotes: 0

Related Questions