Sscanf Problems with C

Question

Hi I am having problems with sscanf. I am just trying to write a simple test program to help me understand how it works. The problem arises when writing to differents variables with sscanf. Here is what their values should be:

IP=175.85.10.147

number=2589

email = [email protected]

 #include <stdio.h> #include <stdlib.h> int main() { char *toSend = "175.85.10.147:2589:[email protected]"; int *number; char IP[200]; char email[300]; sscanf(toSend, "%[^:]: %i%[^:]: ", IP, number, email); printf("%s", IP); printf("%i", number); printf("%s", email); return 0; }

The IP it prints correct.

The number doesn't print correctly, which might be related to this warning I'm getting at compile time: format '%i' expects argument of type 'int' but argument 2 has type 'int *'.

The email variable just contains bizarre characters for some reason.

You passed a pointer to an int as an argument to a function that takes an int in that position. remove the * from the variable declaration so that it reads int number; and see if that works. — ocket8888
– ocket8888, Commented Jan 18, 2017 at 23:20
Well, let's deal with the warning first. %i expects an int and you're giving it number which is int*. — Ivaylo Valchev
– Ivaylo Valchev, Commented Jan 18, 2017 at 23:20
int *number; --> int number;, sscanf(toSend,"%199[^:]: %i:%299s", IP, &number, email); — BLUEPIXY
– BLUEPIXY, Commented Jan 18, 2017 at 23:21
0100 means sixty-four, right? if you disagree use %d instead if %i — Jasen
– Jasen, Commented Jan 18, 2017 at 23:46
@Jasen: you are right, %i will magically parse 0 prefixed numbers as octal. — Jongware
– Jongware, Commented Jan 18, 2017 at 23:48

Ed Heal · Accepted Answer · 2017-01-19 00:43:16Z

4

You need some memory to store number

i.e. change

int *number;

to

int number;

Then use

 sscanf(toSend,"%[^:]:%i:%[^:]",IP, &number, email);

I have also correct the typos - here is the code http://ideone.com/hpqGDZ

#include <stdio.h> #include <stdlib.h> #include <assert.h> int main(){ char *toSend = "175.85.10.147:2589:[email protected]"; int number; char IP[200]; char email[300]; if (sscanf(toSend, "%199[^:]:%i:%299[^:]", IP, &number, email) != 3) { return 1; } printf("%s\n", IP); printf("%i\n", number); printf("%s\n", email); return 0; }

edited Jan 19, 2017 at 0:43

answered Jan 18, 2017 at 23:20

Ed Heal

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5 Comments

ocket8888 Over a year ago

I don't think passing a reference to number is correct, that'll still have the type int* won't it?

Ed Heal Over a year ago

@ArnauVanBoschkenArnauB - Please use BLUEPIXY sscanf with the enhancement that avoid buffer overruns

Ed Heal Over a year ago

Yes - Was thinking that myself. - Updated the answer. Not sure if assert is the best way to go - but it will do

Malcolm McLean Over a year ago

assert should only be used for debug runs. It's designed to compile to nothing on release builds. So N = scanf(...) assert(N ==3) is fine, but not to wrap the call.

AnT stands with Russia Over a year ago

Space before %i is redundant. There's absolutely no reason for it to be there.

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