scanf

[Ab]

What does the "%%" format specifier in scanf do? eg if we write

char ch;
scanf("%%", &ch);

what change if any does it make to ch. If it does not whats the use.

 

[Nick Keighley]

What does the "%%" format specifier in scanf do?

expects a % character

eg if we write

char ch;
scanf("%%", &ch);

what change if any does it make to ch.
none

If it does not whats the use.

see above


--
Nick Keighley

"The Real Programmer wants a "you asked for it, you got it"
text editor--complicated, cryptic, powerful, unforgiving,
dangerous. TECO, to be precise."

 

[Richard Bos]

What does the "%%" format specifier in scanf do?

It stops trolls from reading the fscking manual.

HTH; HAND; FOAD.

Richard

 

[Emmanuel Delahaye]

Ab wrote on 19/08/05 :

What does the "%%" format specifier in scanf do? eg if we write

It's the 'escape' value for '%' in a format string.

char ch;
scanf("%%", &ch);

what change if any does it make to ch. If it does not whats the use.

Undefined Behaviour (The number of parameters doesn't match the number
of formaters). Anything could happen.

--
Emmanuel
The C-FAQ: http://www.eskimo.com/~scs/C-faq/faq.html
The C-library: http://www.dinkumware.com/refxc.html

"Mal nommer les choses c'est ajouter du malheur au
monde." -- Albert Camus.

 

[Keith Thompson]

Ab wrote on 19/08/05 :

It's the 'escape' value for '%' in a format string.


Undefined Behaviour (The number of parameters doesn't match the number
of formaters). Anything could happen.

Extra arguments to scanf() are evaluated but are otherwise ignored.
C99 7.19.6.2p2.

 

[Robert Gamble]

Ab wrote on 19/08/05 :

It's the 'escape' value for '%' in a format string.


Undefined Behaviour (The number of parameters doesn't match the number
of formaters). Anything could happen.

If there are insufficient arguments the behavior is undefined, extra
arguments are ignored without invoking undefined behavior. The same
goes for the fprintf functions.

Robert Gamble

 

[Malcolm]

What does the "%%" format specifier in scanf do? eg if we write

char ch;
scanf("%%", &ch);

what change if any does it make to ch. If it does not whats the use.

You are reading some economics data, which contains inflation rates. Since
there are many definitions of inflation, the economist has prepared the data
by appending letters, so for instance Keynes'es definition is 2.6%k whilst
Friedman's definition is expressed as 2.6%f.

If you try to scan this data using scanf(), the %f will be interpreted as a
format conversion specifier. So you need to escape the % sign to indicate
that it is a percentage in the text, not a field specifier. To make it
easier, the %k also has to be escaped.