wscanf

Name

wscanf, fwscanf, swscanf, vwscanf, vswscanf, vfwscanf
- convert formatted wide-character input

Library

libc.lib

Synopsis

#include <stdio.h>

#include <wchar.h>

int wscanf (const wchar_t * restrict format, ...);

int fwscanf (FILE * restrict stream, const wchar_t * restrict format, ...);

int swscanf (const wchar_t * restrict str, const wchar_t * restrict format, ...);

#include <stdarg.h>

int vwscanf (const wchar_t * restrict format, va_list ap);

int vswscanf (const wchar_t * restrict str, const wchar_t * restrict format, va_list ap);

int vfwscanf (FILE * restrict stream, const wchar_t * restrict format, va_list ap);

Return values

These functions return the number of input items assigned, which can be fewer than provided for, or even zero, in the event of a matching failure. Zero indicates that, while there was input available, no conversions were assigned; typically this is due to an invalid input character, such as an alphabetic character for a ‘%d’ conversion. The value EOF is returned if an input failure occurs before any conversion such as an end-of-file occurs. If an error or end-of-file occurs after conversion has begun, the number of conversions which were successfully completed is returned.

Detailed description

The wscanf family of functions scans input according to a format as described below. This format may contain conversion specifiers; the results from such conversions, if any, are stored through the pointer arguments. The wscanf function reads input from the standard input stream stdin, fwscanf reads input from the stream pointer stream, and swscanf reads its input from the wide character string pointed to by str. The vfwscanf function is analogous to vfwprintf and reads input from the stream pointer stream using a variable argument list of pointers. The vwscanf function scans a variable argument list from the standard input and the vswscanf function scans it from a wide character string; these are analogous to the vwprintf and vswprintf functions respectively. Each successive pointer argument must correspond properly with each successive conversion specifier (but see the * conversion below). All conversions are introduced by the % (percent sign) character. The format string may also contain other characters. White space (such as blanks, tabs, or newlines) in the format string match any amount of white space, including none, in the input. Everything else matches only itself. Scanning stops when an input character does not match such a format character. Scanning also stops when an input conversion cannot be made (see below).

Conversions

Following the % character introducing a conversion there may be a number of flag characters, as follows:

*	Suppresses assignment. The conversion that follows occurs as usual, but no pointer is used; the result of the conversion is simply discarded.
hh	Indicates that the conversion will be one of dioux or n and the next pointer is a pointer to a char (rather than int ) .
h	Indicates that the conversion will be one of dioux or n and the next pointer is a pointer to a short int (rather than int ) .
l (ell)	Indicates that the conversion will be one of dioux or n and the next pointer is a pointer to a long int (rather than int ) , that the conversion will be one of a, e, f, or g and the next pointer is a pointer to double (rather than float ) , or that the conversion will be one of c or s and the next pointer is a pointer to an array of wchar_t (rather than char ) .
ll (ell ell)
	Indicates that the conversion will be one of dioux or n and the next pointer is a pointer to a long long int (rather than int ) .
L	Indicates that the conversion will be one of a, e, f, or g and the next pointer is a pointer to long double .
j	Indicates that the conversion will be one of dioux or n and the next pointer is a pointer to a intmax_t (rather than int ) .
t	Indicates that the conversion will be one of dioux or n and the next pointer is a pointer to a ptrdiff_t (rather than int ) .
z	Indicates that the conversion will be one of dioux or n and the next pointer is a pointer to a size_t (rather than int ) .
q	(deprecated.) Indicates that the conversion will be one of dioux or n and the next pointer is a pointer to a long long int (rather than int ) .

In addition to these flags, there may be an optional maximum field width, expressed as a decimal integer, between the % and the conversion. If no width is given, a default of "infinity" is used (with one exception, below); otherwise at most this many characters are scanned in processing the conversion. Before conversion begins, most conversions skip white space; this white space is not counted against the field width.

The following conversions are available:

%	Matches a literal ‘`%`’. That is, "%%" in the format string matches a single input ‘`%`’ character. No conversion is done, and assignment does not occur.
d	Matches an optionally signed decimal integer; the next pointer must be a pointer to int .
i	Matches an optionally signed integer; the next pointer must be a pointer to int . The integer is read in base 16 if it begins with ‘`0x`’ or ‘`0X`’, in base 8 if it begins with ‘`0`’, and in base 10 otherwise. Only characters that correspond to the base are used.
o	Matches an octal integer; the next pointer must be a pointer to unsigned int .
u	Matches an optionally signed decimal integer; the next pointer must be a pointer to unsigned int .
x, X	Matches an optionally signed hexadecimal integer; the next pointer must be a pointer to unsigned int .
a, A, e, E, f, F, g, G
	Matches a floating-point number in the style of wcstod. The next pointer must be a pointer to float (unless l or L is specified.)
s	Matches a sequence of non-white-space wide characters; the next pointer must be a pointer to char , and the array must be large enough to accept the multibyte representation of all the sequence and the terminating `NUL` character. The input string stops at white space or at the maximum field width, whichever occurs first. If an l qualifier is present, the next pointer must be a pointer to wchar_t , into which the input will be placed.
S	The same as ls.
c	Matches a sequence of width count wide characters (default 1); the next pointer must be a pointer to char , and there must be enough room for the multibyte representation of all the characters (no terminating `NUL` is added). The usual skip of leading white space is suppressed. To skip white space first, use an explicit space in the format. If an l qualifier is present, the next pointer must be a pointer to wchar_t , into which the input will be placed.
C	The same as lc.
[	Matches a nonempty sequence of characters from the specified set of accepted characters; the next pointer must be a pointer to char , and there must be enough room for the multibyte representation of all the characters in the string, plus a terminating `NUL` character. The usual skip of leading white space is suppressed. The string is to be made up of characters in (or not in) a particular set; the set is defined by the characters between the open bracket [ character and a close bracket ] character. The set excludes those characters if the first character after the open bracket is a circumflex ^. To include a close bracket in the set, make it the first character after the open bracket or the circumflex; any other position will end the set. To include a hyphen in the set, make it the last character before the final close bracket; some implementations of `wscanf` use "A-Z" to represent the range of characters between ‘`A`’ and ‘`Z`’. The string ends with the appearance of a character not in the (or, with a circumflex, in) set or when the field width runs out. If an l qualifier is present, the next pointer must be a pointer to wchar_t , into which the input will be placed.
p	Matches a pointer value (as printed by ‘`%p`’ in wprintf); the next pointer must be a pointer to void .
n	Nothing is expected; instead, the number of characters consumed thus far from the input is stored through the next pointer, which must be a pointer to int . This is not a conversion, although it can be suppressed with the * flag.

The decimal point character is defined in the program’s locale (category LC_NUMERIC).

For backwards compatibility, a "conversion" of ‘%\0’ causes an immediate return of EOF.

Examples

#include <stdio.h>
#include <wchar.h>
/* Illustrates how to use wscanf API */
int example_wscanf(void)
{
  int rval;
  int input;
 /* Display a message to the user to input an integer */
 wprintf(L"Enter an integer : ");
  /* Read an integer from the standard input */
  rval = wscanf(L"%d", &input);
 
  /* return the number of inputs that were read */
  return(rval);
}

#include <stdio.h>
#include <wchar.h>
/* Illustrates how to use swscanf API */
int example_swscanf(void)
{
  int rval;
  wchar_t wcs[100];
  wchar_t *bufptr = L"abcdefg";
 /* Read a string from the buffer bufptr*/
  rval = swscanf(bufptr, L"%s", wcs);
 
  /* The string that was read into wcs is printed */
  wprintf(L"%s",wcs);
 
  /* return the number of inputs that were read */
  return(rval);
}

#include <stdio.h>
#include <wchar.h>
/* Illustrates how to use fwscanf API */
int example_fwscanf(void)
{
  FILE *fp = NULL;
  int retval;
  wchar_t wcs[100];
   
  /* open the file for writing*/
  fp = fopen("write.txt","w");
  if(fp == NULL)
  {
    wprintf(L"Error: File open\n");
    return (-1);
  }
 /* Read a string from fp*/
  rval = fwscanf(fp, L"%s", wcs);
 
 /* Close the file that was opened */
  fclose(fp);
 
  /* return the number of inputs that were read */
  return(rval);
}

#include <stdio.h>
#include <wchar.h>
/* Illustrates how to use vwscanf API */
int example_vwscanf(va_list arg)
{
  int retval;
    
 /* Read a string from standard input */
  rval = vwscanf(L"%s", arg);
 
  /* return the number of inputs that were read */
  return(rval);
}

#include <stdio.h>
#include <wchar.h>
/* Illustrates how to use vswscanf API */
int example_vswscanf(va_list arg)
{
  int retval;
  wchar_t bufptr = L"abc";
    
 /* Read a string from bufptr */
  rval = vswscanf(bufptr, L"%s", arg);
 
  /* return the number of inputs that were read */
  return(rval);
}

#include <stdio.h>
#include <wchar.h>
/* Illustrates how to use vfwscanf API */
int example_vfwscanf(va_list arg)
{
  FILE *fp = NULL;
  int retval;
    
  /* open the file for writing*/
  fp = fopen("write.txt","w");
  if(fp == NULL)
  {
    wprintf(L"Error: File open\n");
    return (-1);
  }
 /* Read a string */
  rval = vfwscanf(fp, L"%s", arg);
 
  /* Close the file that was opened */
  fclose(fp);
 
  /* return the number of inputs that were read */
  return(rval);
}

Security considerations

Please refer scanf

Limitations

All these API’s don’t support long double length modifiers.

Bugs

In addition to the bugs documented in scanf, wscanf does not support the "A-Z" notation for specifying character ranges with the character class conversion ('%[').

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