WPRINTF(3) | Library Functions Manual | WPRINTF(3)

# NAME

`wprintf`, `fwprintf`, `swprintf`, `vwprintf`, `vfwprintf`, `vswprintf` —
formatted wide character output conversion

# LIBRARY

Standard C Library (libc, -lc)

# SYNOPSIS

`#include <stdio.h>`
`#include <wchar.h>`

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

int
`swprintf`(wchar_t * restrict ws, size_t n, const wchar_t * restrict format, ...);

int
`wprintf`(const wchar_t * restrict format, ...);

`#include <stdarg.h>`

int
`vfwprintf`(FILE * restrict stream, const wchar_t * restrict, va_list ap);

int
`vswprintf`(wchar_t * restrict ws, size_t n, const wchar_t *restrict format, va_list ap);

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

# DESCRIPTION

The `wprintf`() family of functions produces output according to a format as described below. The `wprintf`() and `vwprintf`() functions write output to `stdout`, the standard output stream; `fwprintf`() and `vfwprintf`() write output to the given output stream; `swprintf`() and `vswprintf`() write to the wide-character string ws.

These functions write the output under the control of a format string that specifies how subsequent arguments (or arguments accessed via the variable-length argument facilities of stdarg(3)) are converted for output.

The `swprintf`() and `vswprintf`() functions will fail if n or more wide characters were requested to be written,

The format string is composed of zero or more directives: ordinary characters (not `%`), which are copied unchanged to the output stream; and conversion specifications, each of which results in fetching zero or more subsequent arguments. Each conversion specification is introduced by the `%` character. The arguments must correspond properly (after type promotion) with the conversion specifier. After the `%`, the following appear in sequence:

- An optional field, consisting of a decimal digit string followed by a `$`, specifying the next argument to access. If this field is not provided, the argument following the last argument accessed will be used. Arguments are numbered starting at `1`. If unaccessed arguments in the format string are interspersed with ones that are accessed the results will be indeterminate.
- Zero or more of the following flags:
  ‘`#`’
    The value should be converted to an “alternate form”. For `c`, `d`, `i`, `n`, `p`, `s`, and `u` conversions, this option has no effect. For `o` conversions, the precision of the number is increased to force the first character of the output string to a zero (except if a zero value is printed with an explicit precision of zero). For `x` and `X` conversions, a non-zero result has the string ‘`0x`’ (or ‘`0X`’ for `X` conversions) prepended to it. For `a`, `A`, `e`, `E`, `f`, `F`, `g`, and `G` conversions, the result will always contain a decimal point, even if no digits follow it (normally, a decimal point appears in the results of those conversions only if a digit follows). For `g` and `G` conversions, trailing zeros are not removed from the result as they would otherwise be.
  ‘`0`’ (zero)
    Zero padding. For all conversions except `n`, the converted value is padded on the left with zeros rather than blanks. If a precision is given with a numeric conversion (`d`, `i`, `o`, `u`, `i`, `x`, and `X`), the `0` flag is ignored.
  ‘`-`’
    A negative field width flag; the converted value is to be left adjusted on the field boundary. Except for `n` conversions, the converted value is padded on the right with blanks, rather than on the left with blanks or zeros. A `-` overrides a `0` if both are given.
  ‘ ’ (space)
    A blank should be left before a positive number produced by a signed conversion (`a`, `A`, `d`, `e`, `E`, `f`, `F`, `g`, `G`, or `i`).
  ‘`+`’
    A sign must always be placed before a number produced by a signed conversion. A `+` overrides a space if both are used.
  ‘`'`’
    Decimal conversions (`d`, `u`, or `i`) or the integral portion of a floating point conversion (`f` or `F`) should be grouped and separated by thousands using the non-monetary separator returned by localeconv(3).
- An optional decimal digit string specifying a minimum field width. If the converted value has fewer characters than the field width, it will be padded with spaces on the left (or right, if the left-adjustment flag has been given) to fill out the field width.
- An optional precision, in the form of a period `.` followed by an optional digit string. If the digit string is omitted, the precision is taken as zero. This gives the minimum number of digits to appear for `d`, `i`, `o`, `u`, `x`, and `X` conversions, the number of digits to appear after the decimal-point for `a`, `A`, `e`, `E`, `f`, and `F` conversions, the maximum number of significant digits for `g` and `G` conversions, or the maximum number of characters to be printed from a string for `s` conversions.
- An optional length modifier, that specifies the size of the argument. The following length modifiers are valid for the `d`, `i`, `n`, `o`, `u`, `x`, or `X` conversion:

  Modifier | `d`, `i` | `o`, `u`, `x`, `X` | `n`
  `hh` | signed char | unsigned char | signed char *
  `h` | short | unsigned short | short *
  `l` (ell) | long | unsigned long | long *
  `ll` (ell ell) | long long | unsigned long long | long long *
  `j` | intmax_t | uintmax_t | intmax_t *
  `t` | ptrdiff_t | (see note) | ptrdiff_t *
  `z` | (see note) | size_t | (see note)
  `q` (deprecated) | quad_t | u_quad_t | quad_t *

  Note: the `t` modifier, when applied to a `o`, `u`, `x`, or `X` conversion, indicates that the argument is of an unsigned type equivalent in size to a ptrdiff_t. The `z` modifier, when applied to a `d` or `i` conversion, indicates that the argument is of a signed type equivalent in size to a size_t. Similarly, when applied to an `n` conversion, it indicates that the argument is a pointer to a signed type equivalent in size to a size_t.

  The following length modifier is valid for the `a`, `A`, `e`, `E`, `f`, `F`, `g`, or `G` conversion:

  Modifier | `a`, `A`, `e`, `E`, `f`, `F`, `g`, `G`
  `L` | long double

  The following length modifier is valid for the `c` or `s` conversion:

  Modifier | `c` | `s`
  `l` (ell) | wint_t | wchar_t *

- A character that specifies the type of conversion to be applied.

A field width or precision, or both, may be indicated by an asterisk ‘`*`’ or an asterisk followed by one or more decimal digits and a ‘`$`’ instead of a digit string. In this case, an int argument supplies the field width or precision. A negative field width is treated as a left adjustment flag followed by a positive field width; a negative precision is treated as though it were missing. If a single format directive mixes positional (`nn$`) and non-positional arguments, the results are undefined.

The conversion specifiers and their meanings are:

`diouxX`
  The int (or appropriate variant) argument is converted to signed decimal (`d` and `i`), unsigned octal (`o`), unsigned decimal (`u`), or unsigned hexadecimal (`x` and `X`) notation. The letters “`abcdef`” are used for `x` conversions; the letters “`ABCDEF`” are used for `X` conversions. The precision, if any, gives the minimum number of digits that must appear; if the converted value requires fewer digits, it is padded on the left with zeros.
`DOU`
  The long int argument is converted to signed decimal, unsigned octal, or unsigned decimal, as if the format had been `ld`, `lo`, or `lu` respectively. These conversion characters are deprecated, and will eventually disappear.
`eE`
  The double argument is rounded and converted in the style [-]d`.`ddd `e±`dd where there is one digit before the decimal-point character and the number of digits after it is equal to the precision; if the precision is missing, it is taken as 6; if the precision is zero, no decimal-point character appears. An `E` conversion uses the letter ‘`E`’ (rather than ‘`e`’) to introduce the exponent. The exponent always contains at least two digits; if the value is zero, the exponent is 00.

  For `a`, `A`, `e`, `E`, `f`, `F`, `g`, and `G` conversions, positive and negative infinity are represented as `inf` and `-inf` respectively when using the lowercase conversion character, and `INF` and `-INF` respectively when using the uppercase conversion character. Similarly, NaN is represented as `nan` when using the lowercase conversion, and `NAN` when using the uppercase conversion.

`fF`
  The double argument is rounded and converted to decimal notation in the style [-]ddd`.`ddd, where the number of digits after the decimal-point character is equal to the precision specification. If the precision is missing, it is taken as 6; if the precision is explicitly zero, no decimal-point character appears. If a decimal point appears, at least one digit appears before it.
`gG`
  The double argument is converted in style `f` or `e` (or `F` or `E` for `G` conversions). The precision specifies the number of significant digits. If the precision is missing, 6 digits are given; if the precision is zero, it is treated as 1. Style `e` is used if the exponent from its conversion is less than -4 or greater than or equal to the precision. Trailing zeros are removed from the fractional part of the result; a decimal point appears only if it is followed by at least one digit.
`aA`
  The double argument is converted to hexadecimal notation in the style [-]`0x` h`.`hhhp[±]d, where the number of digits after the hexadecimal-point character is equal to the precision specification. If the precision is missing, it is taken as enough to exactly represent the floating-point number; if the precision is explicitly zero, no hexadecimal-point character appears. This is an exact conversion of the mantissa+exponent internal floating point representation; the [-]`0x` h`.`hhh portion represents exactly the mantissa; only denormalized mantissas have a zero value to the left of the hexadecimal point. The `p` is a literal character ‘`p`’; the exponent is preceded by a positive or negative sign and is represented in decimal, using only enough characters to represent the exponent. The `A` conversion uses the prefix “`0X`” (rather than “`0x`”), the letters “`ABCDEF`” (rather than “`abcdef`”) to represent the hex digits, and the letter ‘`P`’ (rather than ‘`p`’) to separate the mantissa and exponent.
`C`
  Treated as `c` with the `l` (ell) modifier.
`c`
  The int argument is converted to an unsigned char, then to a wchar_t as if by btowc(3), and the resulting character is written.

  If the `l` (ell) modifier is used, the wint_t argument is converted to a wchar_t and written.

`S`
  Treated as `s` with the `l` (ell) modifier.
`s`
  The char * argument is expected to be a pointer to an array of character type (pointer to a string) containing a multibyte sequence. Characters from the array are converted to wide characters and written up to (but not including) a terminating `NUL` character; if a precision is specified, no more than the number specified are written. If a precision is given, no null character need be present; if the precision is not specified, or is greater than the size of the array, the array must contain a terminating `NUL` character.

  If the `l` (ell) modifier is used, the wchar_t * argument is expected to be a pointer to an array of wide characters (pointer to a wide string). Each wide character in the string is written. Wide characters from the array are written up to (but not including) a terminating wide `NUL` character; if a precision is specified, no more than the number specified are written (including shift sequences). If a precision is given, no null character need be present; if the precision is not specified, or is greater than the number of characters in the string, the array must contain a terminating wide `NUL` character.

`p`
  The void * pointer argument is printed in hexadecimal (as if by ‘`%#x`’ or ‘`%#lx`’).
`n`
  The number of characters written so far is stored into the integer indicated by the int * (or variant) pointer argument. No argument is converted.
`%`
  A ‘`%`’ is written. No argument is converted. The complete conversion specification is ‘`%%`’.

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

In no case does a non-existent or small field width cause truncation of a numeric field; if the result of a conversion is wider than the field width, the field is expanded to contain the conversion result.

# RETURN VALUES

These functions return the number of characters printed (not including the trailing ‘`\0`’ used to end output to strings).

# SEE ALSO

btowc(3), fputws(3), printf(3), putwc(3), setlocale(3), wcsrtombs(3), wscanf(3)

# STANDARDS

The `wprintf`(), `fwprintf`(), `swprintf`(), `vwprintf`(), `vfwprintf`() and `vswprintf`() functions conform to ISO/IEC 9899:1999 (“ISO C99”).

# SECURITY CONSIDERATIONS

Subject to the caveats noted in the printf(3).

April 30, 2010 | NetBSD 9.2