printf, _printf_l, wprintf, _wprintf_l

Prints formatted output to the standard output stream. More secure versions of these functions are available; see printf_s, _printf_s_l, wprintf_s, _wprintf_s_l.

Syntax

int printf(
   const char *format [,
   argument]...
);
int _printf_l(
   const char *format,
   locale_t locale [,
   argument]...
);
int wprintf(
   const wchar_t *format [,
   argument]...
);
int _wprintf_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. If format is NULL, the 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. If EOF (0xFFFF) is encountered in argument, the function returns -1.

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

Remarks

The printf 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. printf and fprintf behave identically except that printf writes output to stdout rather than to a destination of type FILE.

wprintf is a wide-character version of printf; format is a wide-character string. wprintf and printf behave identically if the stream is opened in ANSI mode. printf does not 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 printf printf wprintf

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("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 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.

Generic-Text Routine Mappings

Tchar.h routine _UNICODE and _MBCS not defined _MBCS defined _UNICODE defined
_tprintf printf printf wprintf
_tprintf_l _printf_l _printf_l _wprintf_l

Requirements

Routine Required header
printf, _printf_l <stdio.h>
wprintf, _wprintf_l <stdio.h> or <wchar.h>

The console is not supported in Universal Windows Platform (UWP) 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 UWP apps. For additional compatibility information, see Compatibility.

Example

// crt_printf.c
// This program uses the printf and wprintf functions
// to produce formatted output.

#include <stdio.h>

int main( void )
{
   char     ch = 'h',
            *string = "computer";
   wchar_t  wch = L'w',
            *wstring = L"Unicode";
   int      count = -9234;
   double   fp = 251.7366;

   // Display integers
   printf( "Integer formats:\n"
           "   Decimal: %d  Justified: %.6d  "
           "Unsigned: %u\n",
           count, count, count, count );

   // Display decimals
   printf( "Decimal %d as:\n   Hex: %Xh  "
           "C hex: 0x%x  Octal: %o\n",
            count, count, count, count );

   // Display in different radixes
   printf( "Digits 10 equal:\n   Hex: %i  "
           "Octal: %i  Decimal: %i\n",
            0x10, 010, 10 );

   // Display characters
   printf("Characters in field (1):\n"
          "%10c%5hc%5C%5lc\n",
          ch, ch, wch, wch);
   wprintf(L"Characters in field (2):\n"
           L"%10C%5hc%5c%5lc\n",
           ch, ch, wch, wch);

   // Display strings
   printf("Strings in field (1):\n%25s\n"
          "%25.4hs\n   %S%25.3ls\n",
          string, string, wstring, wstring);
   wprintf(L"Strings in field (2):\n%25S\n"
           L"%25.4hs\n   %s%25.3ls\n",
           string, string, wstring, wstring);

   // Display real numbers
   printf("Real numbers:\n   %f %.2f %e %E\n",
          fp, fp, fp, fp );

   // Display pointer
   printf( "\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:   0012FF3C

See also

Floating-Point Support
Stream I/O
Locale
fopen, _wfopen
_fprintf_p, _fprintf_p_l, _fwprintf_p, _fwprintf_p_l
scanf, _scanf_l, wscanf, _wscanf_l
sprintf, _sprintf_l, swprintf, _swprintf_l, __swprintf_l
vprintf Functions
_set_output_format