CODEWITHSUNDEEP
ccstringscanfc-strings
Ethan
Ethan

Reputation: 1266

sscanf with less arguments than specified?

So I'm wondering how sscanf functions when faced with a line like this:

sscanf(input_string, "%s %s %s", cmd1, cmd2, cmd3);

But say the input_string only contains 1 string token. What values are assigned to cmd2 and cmd3? Is there an error thrown?

I'm using the GNU C compiler.

Upvotes: 2

Views: 932

Answers (2)

Jerry Coffin
Jerry Coffin

Reputation: 490158

Nothing will be assigned to the extra parameters. The return from sscanf tells you how many conversions were done successfully, so in this case it would return 1. You typically just compare to the number you expect, and assume the input is bad otherwise:

if (3 != sscanf(input_string,"%s %s %s", cmd1, cmd2, cmd3))
    fprintf(stderr, "Badly formatted input (expecting three strings)\n");

When you're reading from a file, you often want to execute in a loop until you get correct input:

while (3 != scanf("%s %s %s", cmd1, cmd2, cmd3))
    fprintf(stderr, "Please enter 3 strings:");

Upvotes: 4

001
001

Reputation: 13533

http://www.cplusplus.com/reference/clibrary/cstdio/sscanf/

On success, the function returns the number of items in the argument list successfully filled. This count can match the expected number of items or be less -even zero- in the case of a matching failure. In the case of an input failure before any data could be successfully interpreted, EOF is returned.

Upvotes: 2

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