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scanf, _scanf_l, wscanf, _wscanf_l

  • Article

Reads formatted data from the standard input stream. More secure versions of these functions are available; see scanf_s, _scanf_s_l, wscanf_s, _wscanf_s_l.

Note

In Visual Studio 2015 The printf and scanf family of functions were declared as inline and moved to the <stdio.h> and <conio.h> headers. If you are migrating older code you might see Linker Error LNK2019 in connection with these functions. For more information, see Visual C++ change history 2003 - 2015.

Syntax

int scanf(
   const char *format [,
   argument]...
);
int _scanf_l(
   const char *format,
   _locale_t locale [,
   argument]...
);
int wscanf(
   const wchar_t *format [,
   argument]...
);
int _wscanf_l(
   const wchar_t *format,
   _locale_t locale [,
   argument]...
);

Parameters

format
Format control string.

argument
Optional arguments.

locale
The locale to use.

Return value

Returns the number of fields successfully converted and assigned; the return value doesn't include fields that were read but not assigned. A return value of 0 indicates that no fields were assigned.

If format is a NULL pointer, the invalid parameter handler is invoked, as described in Parameter validation. If execution is allowed to continue, these functions return EOF and set errno to EINVAL.

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

Remarks

The scanf function reads data from the standard input stream stdin and writes the data into the location given by argument. Each argument must be a pointer to a variable of a type that corresponds to a type specifier in format. If copying takes place between strings that overlap, the behavior is undefined.

Important

When reading a string with scanf, always specify a width for the %s format (for example, %32s instead of %s); otherwise, improperly formatted input can easily cause a buffer overrun. Alternately, consider using scanf_s, _scanf_s_l, wscanf_s, _wscanf_s_l or fgets.

wscanf is a wide-character version of scanf; the format argument to wscanf is a wide-character string. wscanf and scanf behave identically if the stream is opened in ANSI mode. scanf doesn't currently support input from 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 and _MBCS not defined _MBCS defined _UNICODE defined
_tscanf scanf scanf wscanf
_tscanf_l _scanf_l _scanf_l _wscanf_l

For more information, see Format specification fields: scanf and wscanf functions.

Requirements

Routine Required header
scanf, _scanf_l <stdio.h>
wscanf, _wscanf_l <stdio.h> or <wchar.h>

The console isn't 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 more compatibility information, see Compatibility.

Example

// crt_scanf.c
// compile with: /W3
// This program uses the scanf and wscanf functions
// to read formatted input.

#include <stdio.h>

int main( void )
{
   int   i, result;
   float fp;
   char  c, s[81];
   wchar_t wc, ws[81];
   result = scanf( "%d %f %c %C %80s %80S", &i, &fp, &c, &wc, s, ws ); // C4996
   // Note: scanf and wscanf are deprecated; consider using scanf_s and wscanf_s
   printf( "The number of fields input is %d\n", result );
   printf( "The contents are: %d %f %c %C %s %S\n", i, fp, c, wc, s, ws);
   result = wscanf( L"%d %f %hc %lc %80S %80ls", &i, &fp, &c, &wc, s, ws ); // C4996
   wprintf( L"The number of fields input is %d\n", result );
   wprintf( L"The contents are: %d %f %C %c %hs %s\n", i, fp, c, wc, s, ws);
}

71 98.6 h z Byte characters
36 92.3 y n Wide characters

The number of fields input is 6
The contents are: 71 98.599998 h z Byte characters
The number of fields input is 6
The contents are: 36 92.300003 y n Wide characters

See also

Math and floating-point support
Stream I/O
Locale
fscanf, _fscanf_l, fwscanf, _fwscanf_l
printf, _printf_l, wprintf, _wprintf_l
sprintf, _sprintf_l, swprintf, _swprintf_l, __swprintf_l
sscanf, _sscanf_l, swscanf, _swscanf_l