printf的返回值

引自MSDN:

printf, wprintf

Print formatted output to the standard output stream.

int printf( const char *format [, argument]... );

int wprintf( const wchar_t *format [,argument]... );

RoutineRequired HeaderCompatibilityprintf<stdio.h>ANSI, Win 95, Win NTwprintf<stdio.h> or <wchar.h>ANSI, Win 95, Win NT

For additional compatibility information, see Compatibility in the Introduction.

Libraries

LIBC.LIBSingle thread static library, retail versionLIBCMT.LIBMultithread static library, retail versionMSVCRT.LIBImport library for MSVCRT.DLL, retail version

Return Value

Each of these functions returns the number of characters printed, or a negative value if an error occurs.

Parameters

format

Format control

argument

Optional arguments

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 thatprintf writes output to stdout rather than to a destination of typeFILE.

wprintf is a wide-character version of printf;format is a wide-character string. wprintf and printf behave identically otherwise.

Generic-Text Routine Mappings

TCHAR.H Routine _UNICODE & _MBCS Not Defined_MBCS Defined_UNICODE Defined_tprintfprintfprintfwprintf

The format argument consists of ordinary characters, escape sequences, and (if arguments followformat) format specifications. The ordinary characters and escape sequences are copied tostdout 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. Whenprintf encounters the first format specification (if any), it converts the value of the first argument afterformat 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.

Example

/* PRINTF.C: This program uses the printf and wprintf functions * to produce formatted output. */#include <stdio.h>void 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( "Integer formats:\n"           "\tDecimal: %d  Justified: %.6d  Unsigned: %u\n",           count, count, count, count );   printf( "Decimal %d as:\n\tHex: %Xh  C hex: 0x%x  Octal: %o\n",            count, count, count, count );   /* Display in different radixes. */   printf( "Digits 10 equal:\n\tHex: %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%10C%5hc%5c%5lc\n", ch, ch, wch, wch);   /* Display strings. */   printf("Strings in field (1):\n%25s\n%25.4hs\n\t%S%25.3ls\n",   string, string, wstring, wstring);   wprintf(L"Strings in field (2):\n%25S\n%25.4hs\n\t%s%25.3ls\n",       string, string, wstring, wstring);   /* Display real numbers. */   printf( "Real numbers:\n\t%f %.2f %e %E\n", fp, fp, fp, fp );   /* Display pointer. */   printf( "\nAddress as:\t%p\n", &count);   /* Count characters printed. */   printf( "\nDisplay to here:\n" );   printf( "1234567890123456%n78901234567890\n", &count );   printf( "\tNumber displayed: %d\n\n", count );}

Output

Integer formats:   Decimal: -9234  Justified: -009234  Unsigned: 4294958062Decimal -9234 as:   Hex: FFFFDBEEh  C hex: 0xffffdbee  Octal: 37777755756Digits 10 equal:   Hex: 16  Octal: 8  Decimal: 10Characters in field (1):         h    h    w    wCharacters in field (2):         h    h    w    wStrings in field (1):                 computer                     comp   Unicode                      UniStrings in field (2):                 computer                     comp   Unicode                      UniReal numbers:   251.736600 251.74 2.517366e+002 2.517366E+002Address as:   0012FFACDisplay to here:123456789012345678901234567890   Number displayed: 16