_set_printf_count_output
The new home for Visual Studio documentation is Visual Studio 2017 Documentation on docs.microsoft.com.
The latest version of this topic can be found at _set_printf_count_output.
Enable or disable support of the %n format in printf, _printf_l, wprintf, _wprintf_l-family functions.
Syntax
int _set_printf_count_output(
int enable
);
Parameters
enable
A non-zero value to enable %n support, 0 to disable %n support.
Property Value/Return Value
The state of %n support before calling this function: non-zero if %n support was enabled, 0 if it was disabled.
Remarks
Because of security reasons, support for the %n format specifier is disabled by default in printf and all its variants. If %n is encountered in a printf format specification, the default behavior is to invoke the invalid parameter handler as described in Parameter Validation. Calling _set_printf_count_output with a non-zero argument will cause printf-family functions to interpret %n as described in printf Type Field Characters.
Requirements
| Routine | Required header |
|---|---|
_set_printf_count_output |
<stdio.h> |
For additional compatibility information, see Compatibility in the Introduction.
Example
// crt_set_printf_count_output.c
#include <stdio.h>
int main()
{
int e;
int i;
e = _set_printf_count_output( 1 );
printf( "%%n support was %sabled.\n",
e ? "en" : "dis" );
printf( "%%n support is now %sabled.\n",
_get_printf_count_output() ? "en" : "dis" );
printf( "12345%n6789\n", &i ); // %n format should set i to 5
printf( "i = %d\n", i );
}
Output
%n support was disabled.
%n support is now enabled.
123456789
i = 5
NET Framework Equivalent
Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.