doubts on scanf("%100[^\n]%*[^\n]", buff);

[lovecreatesbea...]

I've read some post on sent by pete and other experts, and have doubts
on following lines of code.

1.
I think the xstr macro isn't needed, is it safe to just use the str
macro in the following scanf statement instead of xstr?

#define STRINGLENGTH 100
#define str(x) # x
#define xstr(x) str(x)

scanf("%" xstr(STRINGLENGTH) "[^\n]%*[^\n]", string);
getchar();

2.
The following scanf is the equivalent of the above scanf. If the users
input 200 characters at terminal, the chars 101~200 remains in stdin
and the next getchar call just read and discard one char, and there
are 99 characters still remains in stdin. Am I right? Masters, can you
teach me.

scanf("%100[^\n]%*[^\n]", buff);
getchar();

 

[Eric Sosman]

(e-mail address removed) wrote On 03/29/07 12:03,:

I've read some post on sent by pete and other experts, and have doubts
on following lines of code.

1.
I think the xstr macro isn't needed, is it safe to just use the str
macro in the following scanf statement instead of xstr?

#define STRINGLENGTH 100
#define str(x) # x
#define xstr(x) str(x)

scanf("%" xstr(STRINGLENGTH) "[^\n]%*[^\n]", string);
getchar();

No, changing the final xstr to str is not "safe." To
see why, try printing the string to see what it looks like:

puts("%" xstr(STRINGLENGTH) "[^\n]%*[^\n]");

.... and again with the change you think is "safe." See
a difference?

2.
The following scanf is the equivalent of the above scanf. If the users
input 200 characters at terminal, the chars 101~200 remains in stdin
and the next getchar call just read and discard one char, and there
are 99 characters still remains in stdin. Am I right? Masters, can you
teach me.

scanf("%100[^\n]%*[^\n]", buff);
getchar();

You're ignoring the effect of the "%*[^\n]" part.