Scan string and integer from file in C

Question

I'm trying to put values from a file into variables. I have a fruits.txt file with the following data.

bananas,5
apples,3
kiwi,7

The comma separates the name of the fruit from the price. My goal is to put the name into a string called fruit and the price into an int called price, move the file pointer to the next line, then print it.

FILE * fptr = fopen("fruit.txt", "r");
char fruit[10];
int price = 0;

fscanf(fptr, "%s,%d\n", fruit, &price);
printf("%s,%d\n", fruit, price);

fclose(fptr);

Is what I have so far. However, my output is bananas,5,0. It seems like it is doing the first part correctly but then adding another ,0. Does anyone know how to fix this?

You could try while(fscanf(fptr, "%9s,%d", fruit, &price) == 2) but please be more generous with the size of the string, and, restrict the input length. And there is no need to pick off the trailing newline: both %s and %d ignore leading whitespace. — Weather Vane
– Weather Vane, Commented Oct 6, 2018 at 21:15
& you should have edited it instead asking a new one to the same topic. — Swordfish
– Swordfish, Commented Oct 6, 2018 at 21:15
@WeatherVane %s eats delimiter too so he should better use [^,]. — kiran Biradar
– kiran Biradar, Commented Oct 6, 2018 at 21:43

kiran Biradar · Accepted Answer · 2018-10-06 21:44:20Z

4

my output is 'bananas,5,0'. It seems like it is doing the first part correctly but then adding another ,0.

Because %s eats your delimiter(,) too, hence putting complete bananas,5 into fruit variable.

If you had checked the return value from fscanf it was just returning 1 and it was not reading %d into price variable.

Solution:

You could just use [^,] to read the string using , as delimiter and put fscanf in while loop checking return value for 2.

Sample code.

FILE * fptr = fopen("fruit.txt", "r");
char fruit[10];
int price = 0;

while(fscanf(fptr, "%9[^,],%d%*[\n]", fruit, &price) == 2)
    printf("%s,%d\n", fruit, price);

fclose(fptr);

edited Oct 6, 2018 at 21:44

answered Oct 6, 2018 at 21:31

kiran Biradar

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5 Comments

kiran Biradar Over a year ago

@User9123 %9 means fscanf should only read max of 9 char. That is done to avoid buffer overflow since you have declared fruit[10]

kiran Biradar Over a year ago

@User9123 and %* means read the input but do not assign it to any arguments in fscanf. That is done to eat up the input until reaching end of the line.

kiran Biradar Over a year ago

@Swordfish my comment got removed I don't know how.

Swordfish Over a year ago

@kiranBiradar I'm innocent.

kiran Biradar Over a year ago

@Swordfish yes you are! Some moderator must have removed it.

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