mbtowc(3)

mbtowc3

Convert a character to a wide-character code

Usage

#include <stdlib.h>

int

mbtowc(wchar_t * restrict wcharp, const char * restrict mbchar, size_t nbytes);

Library

Standard C Library (libc, -lc)

Overview

The mbtowc() function converts a multibyte character mbchar into a wide character according to the current conversion state, and stores the result in the object pointed to by wcharp. Up to nbytes bytes are examined.

A call with a null mbchar pointer returns nonzero if the current encoding requires shift states, zero otherwise; if shift states are required, the shift state is reset to the initial state.

Return values

If mbchar is NULL, the mbtowc() function returns nonzero if shift states are supported, zero otherwise.

Otherwise, if mbchar is not a null pointer, mbtowc() either returns 0 if mbchar represents the null wide character, or returns the number of bytes processed in mbchar, or returns -1 if no multibyte character could be recognized or converted. In this case, mbtowc(Ns, 's) internal conversion state is undefined.

Errors

The mbtowc() function will fail if:

[EILSEQ]

An invalid multibyte sequence was detected.

[EINVAL]

The internal conversion state is invalid.

Releases

83 releases since FreeBSD 2.2.2-RELEASE; the text changed 44 times.

  1. 2.2.2
  2. 2.2.5–3.4
  3. 3.5–3.5.1
  4. 4.0
  5. 4.1–4.2
  6. 4.3
  7. 4.4
  8. 4.5–4.11
  9. 5.0
  10. 5.1
  11. 5.2–5.2.1
  12. 5.3–6.3
  13. 6.4
  14. 7.0
  15. 7.1
  16. 7.2
  17. 7.3
  18. 7.4
  19. 8.0
  20. 8.1
  21. 8.2
  22. 8.3
  23. 8.4
  24. 9.0
  25. 9.1
  26. 9.2
  27. 9.3
  28. 10.0
  29. 10.1
  30. 10.2
  31. 10.3
  32. 10.4
  33. 11.0
  34. 11.1
  35. 11.2
  36. 11.3
  37. 11.4
  38. 12.0
  39. 12.1
  40. 12.2
  41. 12.3
  42. 12.4
  43. 13.0–13.2
  44. 13.3–14.5
  45. 15.0–16.0

Standards

The mbtowc() function conforms to ISO/IEC 9899:1999 (“ISO C99”).

From base 16.0-CURRENT-20261027-61c70dc16a79 in FreeBSD 16.0-CURRENT (2026-10-27). Parsed by carta from the page's mdoc source.