What is the printf format specifier for bool?

c++ c boolean printf
maxschlepzig picture maxschlepzig · Jun 25, 2013 · Viewed 757.8k times · Source

Since ANSI C99 there is _Bool or bool via stdbool.h. But is there also a printf format specifier for bool?

I mean something like in that pseudo code:

bool x = true;
printf("%B\n", x);

which would print:

true

Answer

user529758 picture user529758 · Jun 25, 2013

There is no format specifier for bool types. However, since any integral type shorter than int is promoted to int when passed down to printf()'s variadic arguments, you can use %d:

bool x = true;
printf("%d\n", x); // prints 1

But why not:

printf(x ? "true" : "false");

or, better:

printf("%s", x ? "true" : "false");

or, even better:

fputs(x ? "true" : "false", stdout);

instead?

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