PROLOG

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of
       this interface may differ (consult the corresponding Linux  manual  page  for  details  of
       Linux behavior), or the interface may not be implemented on Linux.

NAME

       mbstowcs — convert a character string to a wide-character string

SYNOPSIS

       #include <stdlib.h>

       size_t mbstowcs(wchar_t *restrict pwcs, const char *restrict s,
           size_t n);

DESCRIPTION

       The functionality described on this reference page is aligned with the ISO C standard. Any
       conflict between the requirements described here and the ISO C standard is  unintentional.
       This volume of POSIX.1‐2017 defers to the ISO C standard.

       The  mbstowcs() function shall convert a sequence of characters that begins in the initial
       shift state from the array pointed to by s into a sequence of corresponding wide-character
       codes  and  shall  store not more than n wide-character codes into the array pointed to by
       pwcs.  No characters that follow a null byte (which is  converted  into  a  wide-character
       code with value 0) shall be examined or converted. Each character shall be converted as if
       by a call to mbtowc(), except that the shift state of mbtowc() is not affected.

       No more than n elements shall be modified in the array pointed to  by  pwcs.   If  copying
       takes place between objects that overlap, the behavior is undefined.

       The  behavior  of  this function shall be affected by the LC_CTYPE category of the current
       locale.  If pwcs is a null pointer, mbstowcs() shall return the length required to convert
       the entire array regardless of the value of n, but no values are stored.

RETURN VALUE

       If  an  invalid character is encountered, mbstowcs() shall return (size_t)-1 and shall set
       errno to indicate the error.

       Otherwise, mbstowcs() shall return the number of the array elements modified (or  required
       if pwcs is null), not including a terminating 0 code, if any. The array shall not be zero-
       terminated if the value returned is n.

ERRORS

       The mbstowcs() function shall fail if:

       EILSEQ An invalid character sequence is detected. In the POSIX locale  an  [EILSEQ]  error
              cannot occur since all byte values are valid characters.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       mblen(), mbtowc(), wctomb(), wcstombs()

       The Base Definitions volume of POSIX.1‐2017, <stdlib.h>

COPYRIGHT

       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1-2017, Standard for Information Technology -- Portable  Operating  System  Interface
       (POSIX),  The  Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by
       the Institute of Electrical and Electronics Engineers, Inc and The  Open  Group.   In  the
       event  of  any  discrepancy  between this version and the original IEEE and The Open Group
       Standard, the original IEEE and The Open Group  Standard  is  the  referee  document.  The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

       Any  typographical  or  formatting errors that appear in this page are most likely to have
       been introduced during the conversion of the source files to man page  format.  To  report
       such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .