Exit from the square bracket] in sscanf

Question

I want to scan strings like

"[25, 28] => 34" 

I wrote a small program to test it:

 #include <cstdlib> #include <iostream> int main() { char* line = "[25, 28] => 34"; char a1[100], a2[100]; int i; sscanf(line, "[%[^,], %[^\]] => %i", a1, a2, &i); std::cout << "a1 = " << a1 <<"\na2 = " << a2 << "\ni = "<<i <<"\n"; return 0; } 

compilation gives

 warning: unknown escape sequence '\]' 

and exit

 a1 = 25 a2 = 28 i = -1073746244 

If I change it to

 sscanf(line, "[%[^,], %[^]] => %i", a1, a2, &i); 

I do not receive compiler complaints, but still

 a1 = 25 a2 = 28 i = -1073746244 

I know that the problem is in the second token, because

 sscanf(line, "[%[^,], %[0123456789]] => %i", a1, a2, &i); 

gives

 a1 = 25 a2 = 28 i = 34 

But I want to use the termination condition for the second token. How to do it?

Answer 1

Do you want to

 sscanf(line, "[%[^,], %[^]]] => %i", a1, a2, &i); 

Pay attention to three consecutive characters ] - the first character that you do not want to match in the set %[ , the second ends the set starting with %[ , and the third matches ] > at the input

Answer 2

As others have said ... I'm not quite sure what you want to do here ...

Assuming things between brackets are always integers, you can simply do:

 int a, b, c; sscanf(line, "[%d, %d] => %d", &a,&b,&c); 

If you really insist on using regular expressions and want some kind of common material to go between the brackets, then you are looking for:

 sscanf(line, "[%[^,], %[^]]] => %d", a1, a2, &i); 

the second regular expression must match all characters except ] at the end. I believe that you previously tried to avoid ] , but this is not necessary, and the compiler throws an error because it does not know how to handle this escape.

In the capture clause for a2 there is 3 ] , because the first says: “do not include this character in the set of matches of characters”, the second closes the set of matches of characters, and the third matches ] in the input [25, 28] => 34 .

If I completely misunderstood your question, I’ll just clarify, and I can reconsider.

Answer 3

It looks like your question basically boils down to "how to include the character ] in scanf scan". It is possible, and you do not need to avoid it. In particular, for this purpose, the language specification states that when the character ] immediately follows the opening character [ or immediately follows the opening character ^ , which ] is considered part of the scan, not a closing bracket. So, in your case, the format specifier should look like "[%[^,], %[^]]] => %i" . No \ .

I see that you understood almost correctly, except that after the second scan you forgot the third character ] .

Answer 4

Sounds to me like a compiler error (or, in fact, a library) (although you need a third right key, not just two). According to the standard (C99, §7.19.6.2):

If the conversion specifier begins with [] or [^], the right bracket symbol is in the scan list, and the next next right bracket symbol is the corresponding right bracket that ends the specification;

Answer 5

can try

 sscanf(line, "[%s, %s] => %d", a1, a2, &i);