CODEWITHSUNDEEP
ccsvparsingscanf
Calmen Chia
Calmen Chia

Reputation: 365

Issues with sscanf in C

I am writing a program that could read a text with csv format and I am having this issue where the sscanf only parses the whole thing as one string when it is separated by ','.

For example, a code snippet below

char str[100] = "Alex,2933,89,";
char name[50] = "";
int id;
double mark;

sscanf(str, "%s,%d,%lf,", name, &id, &mark);
printf("%s\n", name);
printf("%d\n", id);
printf("%f\n", mark);

Output was:

Alex,2933,89,
896
0.000000

Which is clearly not the expected output. But when str is edited to str = "Alex 2933 89 ", the code is giving me the correct output.

The working code:

char str[100] = "Alex 2933 89 ";
char name[50] = "";
int id;
double mark;

sscanf(str, "%s %d %lf ", name, &id, &mark);
printf("%s\n", name);
printf("%d\n", id);
printf("%f\n", mark);

Correct Output:

Alex
2933
89.000000

Can I know how do I fix this?

Upvotes: 1

Views: 263

Answers (1)

chqrlie
chqrlie

Reputation: 144635

%s stops at white space, the fact that you put a , in the format string does not change this behavior. You should use the %[^,] conversion specification.

Change the code this way:

char str[100] = "Alex,2933,89,";
char name[50] = "";
int id;
double mark;

if (sscanf(str, "%49[^,],%d,%lf,", name, &id, &mark) == 3) {
    printf("%s\n", name);
    printf("%d\n", id);
    printf("%f\n", mark);
}

Note however that %[^,] cannot parse empty fields. If the CSV line may contain empty fields, such as ,23,89.0, sscanf() will fail to convert name because no character matches the %[^,] specification. If you have such lines in the source file, you should parse the string fields manually with strchr() or strcspn().

Upvotes: 1

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