printf_s, _printf_s_l, wprintf_s, _wprintf_s_l

Article
12/18/2017

The latest version of this topic can be found at printf_s, _printf_s_l, wprintf_s, _wprintf_s_l.

Prints formatted output to the standard output stream. These versions of printf, _printf_l, wprintf, _wprintf_l have security enhancements, as described in Security Features in the CRT.

Syntax

int printf_s(  
   const char *format [,  
   argument]...   
);  
int _printf_s_l(  
   const char *format,  
   locale_t locale [,  
   argument]...   
);  
int wprintf_s(  
   const wchar_t *format [,  
   argument]...   
);  
int _wprintf_s_l(  
   const wchar_t *format,  
   locale_t locale [,  
   argument]...   
);

Parameters

format
Format control.

argument
Optional arguments.

locale
The locale to use.

Return Value

Returns the number of characters printed, or a negative value if an error occurs.

Remarks

The printf_s function formats and prints a series of characters and values to the standard output stream, stdout. If arguments follow the format string, the format string must contain specifications that determine the output format for the arguments.

The main difference between printf_s and printf is that printf_s checks the format string for valid formatting characters, whereas printf only checks if the format string is a null pointer. If either check fails, an invalid parameter handler is invoked, as described in Parameter Validation. If execution is allowed to continue, the function returns -1 and sets errno to EINVAL.

For information on errno and error codes, see _doserrno, errno, _sys_errlist, and _sys_nerr.

printf_s andfprintf_s behave identically except that printf_s writes output to stdout rather than to a destination of type FILE. For more information, see fprintf_s, _fprintf_s_l, fwprintf_s, _fwprintf_s_l.

wprintf_s is a wide-character version of printf_s; format is a wide-character string. wprintf_s and printf_s behave identically if the stream is opened in ANSI mode. printf_s doesn't currently support output into a UNICODE stream.

The versions of these functions with the _l suffix are identical except that they use the locale parameter passed in instead of the current thread locale.

Generic-Text Routine Mappings

TCHAR.H routine	_UNICODE & _MBCS not defined	_MBCS defined	_unicode defined
`_tprintf_s`	`printf_s`	`printf_s`	`wprintf_s`
`_tprintf_s_l`	`_printf_s_l`	`_printf_s_l`	`_wprintf_s_l`

The format argument consists of ordinary characters, escape sequences, and (if arguments follow format) format specifications. The ordinary characters and escape sequences are copied to stdout in order of their appearance. For example, the line

printf_s("Line one\n\t\tLine two\n");

produces the output

Line one  
        Line two

Format specifications always begin with a percent sign (%) and are read left to right. When printf_s encounters the first format specification (if any), it converts the value of the first argument after format and outputs it accordingly. The second format specification causes the second argument to be converted and output, and so on. If there are more arguments than there are format specifications, the extra arguments are ignored. The results are undefined if there are not enough arguments for all the format specifications.

Important

Ensure that format is not a user-defined string.

Requirements

Routine	Required header
`printf_s`, `_printf_s_l`	<stdio.h>
`wprintf_s`, `_wprintf_s_l`	<stdio.h> or <wchar.h>

The console is not supported in Windows 8.x Store apps. The standard stream handles that are associated with the console—stdin, stdout, and stderr—must be redirected before C run-time functions can use them in Windows 8.x Store apps. For additional compatibility information, see Compatibility.

Example

// crt_printf_s.c  
/* This program uses the printf_s and wprintf_s functions  
 * to produce formatted output.  
 */  
  
#include <stdio.h>  
  
int main( void )  
{  
   char   ch = 'h', *string = "computer";  
   int    count = -9234;  
   double fp = 251.7366;  
   wchar_t wch = L'w', *wstring = L"Unicode";  
  
   /* Display integers. */  
   printf_s( "Integer formats:\n"  
           "   Decimal: %d  Justified: %.6d  Unsigned: %u\n",  
           count, count, count );  
  
   printf_s( "Decimal %d as:\n   Hex: %Xh  C hex: 0x%x  Octal: %o\n",  
            count, count, count, count );  
  
   /* Display in different radixes. */  
   printf_s( "Digits 10 equal:\n   Hex: %i  Octal: %i  Decimal: %i\n",  
            0x10, 010, 10 );  
  
   /* Display characters. */  
  
   printf_s("Characters in field (1):\n%10c%5hc%5C%5lc\n", ch, ch, wch, wch);  
   wprintf_s(L"Characters in field (2):\n%10C%5hc%5c%5lc\n", ch, ch, wch, wch);  
  
   /* Display strings. */  
  
   printf_s("Strings in field (1):\n%25s\n%25.4hs\n   %S%25.3ls\n",  
   string, string, wstring, wstring);  
   wprintf_s(L"Strings in field (2):\n%25S\n%25.4hs\n   %s%25.3ls\n",  
       string, string, wstring, wstring);  
  
   /* Display real numbers. */  
   printf_s( "Real numbers:\n   %f %.2f %e %E\n", fp, fp, fp, fp );  
  
   /* Display pointer. */  
   printf_s( "\nAddress as:   %p\n", &count);  
  
}

Sample Output

Integer formats:  
   Decimal: -9234  Justified: -009234  Unsigned: 4294958062  
Decimal -9234 as:  
   Hex: FFFFDBEEh  C hex: 0xffffdbee  Octal: 37777755756  
Digits 10 equal:  
   Hex: 16  Octal: 8  Decimal: 10  
Characters in field (1):  
         h    h    w    w  
Characters in field (2):  
         h    h    w    w  
Strings in field (1):  
                 computer  
                     comp  
   Unicode                      Uni  
Strings in field (2):  
                 computer  
                     comp  
   Unicode                      Uni  
Real numbers:  
   251.736600 251.74 2.517366e+002 2.517366E+002  
  
Address as:   0012FF78

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