Standard library header <cwchar>

 

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Standard library headers

Language support <cfloat> <climits> <compare> (C++20) <coroutine> (C++20) <csetjmp> <csignal> <cstdarg> <cstddef> <cstdint> (C++11) <cstdlib> <exception> <initializer_list> (C++11)    <limits> <new> <source_location> (C++20) <stdfloat> (C++23) <typeinfo> <version> (C++20) Concepts <concepts> (C++20) Diagnostics <cassert> <cerrno> <debugging> (C++26) <stacktrace> (C++23) <stdexcept> <system_error> (C++11) Memory management <memory> <memory_resource> (C++17) <scoped_allocator> (C++11) Metaprogramming <type_traits> (C++11) <ratio> (C++11)

General utilities <any> (C++17) <bitset> <bit> (C++20) <charconv> (C++17) <expected> (C++23) <format> (C++20) <functional> <optional> (C++17) <tuple> (C++11) <typeindex> (C++11) <utility> <variant> (C++17) Containers <array> (C++11) <deque> <flat_map> (C++23) <flat_set> (C++23) <forward_list> (C++11) <inplace_vector> (C++26)    <list> <map> <mdspan> (C++23) <queue> <set> <span> (C++20) <stack> <unordered_map> (C++11) <unordered_set> (C++11) <vector> Iterators <iterator> Ranges <generator> (C++23) <ranges> (C++20)

Algorithms <algorithm> <numeric> Strings <cctype> <cstring> <cuchar> (C++11) <cwchar> <cwctype> <string_view> (C++17) <string> Text processing <clocale> <codecvt> (C++11/17/26*) <locale> <regex> (C++11) <text_encoding> (C++26)    Numerics <cfenv> (C++11) <cmath> <complex> <linalg> (C++26) <numbers> (C++20) <random> (C++11) <valarray> Time <chrono> (C++11) <ctime> C compatibility <ccomplex> (C++11/17/20*) <ciso646> (until C++20) <cstdalign> (C++11/17/20*) <cstdbool> (C++11/17/20*) <ctgmath> (C++11/17/20*)

Input/output <cinttypes> (C++11) <cstdio> <filesystem> (C++17) <fstream> <iomanip> <iosfwd> <iostream> <ios> <istream> <ostream> <print> (C++23) <spanstream> (C++23) <sstream> <streambuf> <strstream> (C++98/26*) <syncstream> (C++20) Concurrency support <atomic> (C++11) <barrier> (C++20) <condition_variable> (C++11) <future> (C++11) <hazard_pointer> (C++26) <latch> (C++20) <mutex> (C++11) <rcu> (C++26) <semaphore> (C++20) <shared_mutex> (C++14) <stdatomic.h> (C++23) <stop_token> (C++20) <thread> (C++11) Execution support <execution> (C++17)

 

This header was originally in the C standard library as <wchar.h>.

This header is part of the null-terminated wide and multibyte strings libraries. It also provides some C-style I/O functions and conversion from C-style Date.

Macros

NULL	implementation-defined null pointer constant (macro constant)
WEOF	a non-character value of type std::wint_t used to indicate errors (macro constant)
WCHAR_MIN	the smallest valid value of wchar_t (macro constant)
WCHAR_MAX	the largest valid value of wchar_t (macro constant)

Types

mbstate_t	conversion state information necessary to iterate multibyte character strings (class)
size_t	unsigned integer type returned by the sizeof operator (typedef)
wint_t	integer type that can hold any valid wide character and at least one more value
tm	calendar time type (class)

Functions

String manipulation
wcscpy	copies one wide string to another (function)
wcsncpy	copies a certain amount of wide characters from one string to another (function)
wcscat	appends a copy of one wide string to another (function)
wcsncat	appends a certain amount of wide characters from one wide string to another (function)
wcsxfrm	transform a wide string so that wcscmp would produce the same result as wcscoll (function)
String examination
wcslen	returns the length of a wide string (function)
wcscmp	compares two wide strings (function)
wcsncmp	compares a certain amount of characters from two wide strings (function)
wcscoll	compares two wide strings in accordance to the current locale (function)
wcschr	finds the first occurrence of a wide character in a wide string (function)
wcsrchr	finds the last occurrence of a wide character in a wide string (function)
wcsspn	returns the length of the maximum initial segment that consists of only the wide characters found in another wide string (function)
wcscspn	returns the length of the maximum initial segment that consists of only the wide not found in another wide string (function)
wcspbrk	finds the first location of any wide character in one wide string, in another wide string (function)
wcsstr	finds the first occurrence of a wide string within another wide string (function)
wcstok	finds the next token in a wide string (function)
Wide character array manipulation
wmemcpy	copies a certain amount of wide characters between two non-overlapping arrays (function)
wmemmove	copies a certain amount of wide characters between two, possibly overlapping, arrays (function)
wmemcmp	compares a certain amount of wide characters from two arrays (function)
wmemchr	finds the first occurrence of a wide character in a wide character array (function)
wmemset	copies the given wide character to every position in a wide character array (function)
Multibyte/wide character conversion
mbsinit	checks if the std::mbstate_t object represents initial shift state (function)
btowc	widens a single-byte narrow character to wide character, if possible (function)
wctob	narrows a wide character to a single-byte narrow character, if possible (function)
mbrlen	returns the number of bytes in the next multibyte character, given state (function)
mbrtowc	converts the next multibyte character to wide character, given state (function)
wcrtomb	converts a wide character to its multibyte representation, given state (function)
mbsrtowcs	converts a narrow multibyte character string to wide string, given state (function)
wcsrtombs	converts a wide string to narrow multibyte character string, given state (function)
Input/Output
fgetwcgetwc	gets a wide character from a file stream (function)
fgetws	gets a wide string from a file stream (function)
fputwcputwc	writes a wide character to a file stream (function)
fputws	writes a wide string to a file stream (function)
getwchar	reads a wide character from stdin (function)
putwchar	writes a wide character to stdout (function)
ungetwc	puts a wide character back into a file stream (function)
fwide	switches a file stream between wide character I/O and narrow character I/O (function)
wscanffwscanfswscanf	reads formatted wide character input from stdin, a file stream or a buffer (function)
vwscanfvfwscanfvswscanf (C++11)(C++11)(C++11)	reads formatted wide character input from stdin, a file stream or a buffer using variable argument list (function)
wprintffwprintfswprintf	prints formatted wide character output to stdout, a file stream or a buffer (function)
vwprintfvfwprintfvswprintf	prints formatted wide character output to stdout, a file stream or a buffer using variable argument list (function)
String conversions
wcsftime	converts a std::tm object to custom wide string textual representation (function)
wcstolwcstoll	converts a wide string to an integer value (function)
wcstoulwcstoull	converts a wide string to an unsigned integer value (function)
wcstofwcstodwcstold	converts a wide string to a floating-point value (function)

Notes

• NULL is also defined in the following headers:
  • <cstddef>
  • <cstring>
  • <ctime>
  • <clocale>
  • <cstdio>
• std::size_t is also defined in the following headers:
  • <cstddef>
  • <ctime>
  • <cstdio>
• std::wint_t is also defined in the following headers:
  • <cwctype>
• std::tm is also defined in the following headers:
  • <ctime>

Synopsis

namespace std {
  using size_t =    /* see description */; // freestanding
  using mbstate_t = /* see description */; // freestanding
  using wint_t =    /* see description */; // freestanding
 
  struct tm;
 
  int fwprintf(FILE* stream, const wchar_t* format, ...);
  int fwscanf(FILE* stream, const wchar_t* format, ...);
  int swprintf(wchar_t* s, size_t n, const wchar_t* format, ...);
  int swscanf(const wchar_t* s, const wchar_t* format, ...);
  int vfwprintf(FILE* stream, const wchar_t* format, va_list arg);
  int vfwscanf(FILE* stream, const wchar_t* format, va_list arg);
  int vswprintf(wchar_t* s, size_t n, const wchar_t* format, va_list arg);
  int vswscanf(const wchar_t* s, const wchar_t* format, va_list arg);
  int vwprintf(const wchar_t* format, va_list arg);
  int vwscanf(const wchar_t* format, va_list arg);
  int wprintf(const wchar_t* format, ...);
  int wscanf(const wchar_t* format, ...);
  wint_t fgetwc(FILE* stream);
  wchar_t* fgetws(wchar_t* s, int n, FILE* stream);
  wint_t fputwc(wchar_t c, FILE* stream);
  int fputws(const wchar_t* s, FILE* stream);
  int fwide(FILE* stream, int mode);
  wint_t getwc(FILE* stream);
  wint_t getwchar();
  wint_t putwc(wchar_t c, FILE* stream);
  wint_t putwchar(wchar_t c);
  wint_t ungetwc(wint_t c, FILE* stream);
  double wcstod(const wchar_t* nptr, wchar_t** endptr);
  float wcstof(const wchar_t* nptr, wchar_t** endptr);
  long double wcstold(const wchar_t* nptr, wchar_t** endptr);
  long int wcstol(const wchar_t* nptr, wchar_t** endptr, int base);
  long long int wcstoll(const wchar_t* nptr, wchar_t** endptr, int base);
  unsigned long int wcstoul(const wchar_t* nptr, wchar_t** endptr, int base);
  unsigned long long int wcstoull(const wchar_t* nptr, wchar_t** endptr, int base);
  wchar_t* wcscpy(wchar_t* s1, const wchar_t* s2);                // freestanding
  wchar_t* wcsncpy(wchar_t* s1, const wchar_t* s2, size_t n);     // freestanding
  wchar_t* wmemcpy(wchar_t* s1, const wchar_t* s2, size_t n);     // freestanding
  wchar_t* wmemmove(wchar_t* s1, const wchar_t* s2, size_t n);    // freestanding
  wchar_t* wcscat(wchar_t* s1, const wchar_t* s2);                // freestanding
  wchar_t* wcsncat(wchar_t* s1, const wchar_t* s2, size_t n);     // freestanding
  int wcscmp(const wchar_t* s1, const wchar_t* s2);               // freestanding
  int wcscoll(const wchar_t* s1, const wchar_t* s2);
  int wcsncmp(const wchar_t* s1, const wchar_t* s2, size_t n);    // freestanding
  size_t wcsxfrm(wchar_t* s1, const wchar_t* s2, size_t n);
  int wmemcmp(const wchar_t* s1, const wchar_t* s2, size_t n);    // freestanding
  const wchar_t* wcschr(const wchar_t* s, wchar_t c);             // freestanding
  wchar_t* wcschr(wchar_t* s, wchar_t c);                         // freestanding
  size_t wcscspn(const wchar_t* s1, const wchar_t* s2);           // freestanding
  const wchar_t* wcspbrk(const wchar_t* s1, const wchar_t* s2);   // freestanding
  wchar_t* wcspbrk(wchar_t* s1, const wchar_t* s2);               // freestanding
  const wchar_t* wcsrchr(const wchar_t* s, wchar_t c);            // freestanding
  wchar_t* wcsrchr(wchar_t* s, wchar_t c);                        // freestanding
  size_t wcsspn(const wchar_t* s1, const wchar_t* s2);            // freestanding
  const wchar_t* wcsstr(const wchar_t* s1, const wchar_t* s2);    // freestanding
  wchar_t* wcsstr(wchar_t* s1, const wchar_t* s2);                // freestanding
  wchar_t* wcstok(wchar_t* s1, const wchar_t* s2, wchar_t** ptr); // freestanding
  const wchar_t* wmemchr(const wchar_t* s, wchar_t c, size_t n);  // freestanding
  wchar_t* wmemchr(wchar_t* s, wchar_t c, size_t n);              // freestanding
  size_t wcslen(const wchar_t* s);                                // freestanding
  wchar_t* wmemset(wchar_t* s, wchar_t c, size_t n);              // freestanding
  size_t wcsftime(wchar_t* s, size_t maxsize, const wchar_t* format, const tm* timeptr);
  wint_t btowc(int c);
  int wctob(wint_t c);
 
  // multibyte / wide string and character conversion functions
  int mbsinit(const mbstate_t* ps);
  size_t mbrlen(const char* s, size_t n, mbstate_t* ps);
  size_t mbrtowc(wchar_t* pwc, const char* s, size_t n, mbstate_t* ps);
  size_t wcrtomb(char* s, wchar_t wc, mbstate_t* ps);
  size_t mbsrtowcs(wchar_t* dst, const char** src, size_t len, mbstate_t* ps);
  size_t wcsrtombs(char* dst, const wchar_t** src, size_t len, mbstate_t* ps);
}
 
#define NULL      /* see description */ // freestanding
#define WCHAR_MAX /* see description */ // freestanding
#define WCHAR_MIN /* see description */ // freestanding
#define WEOF      /* see description */ // freestanding

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 345	C++98	std::tm was not provided in <cwchar>	provided