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mbsrtowcs(3) — Linux manual page

NAME \|LIBRARY \|SYNOPSIS \|DESCRIPTION \|RETURN VALUE \|ATTRIBUTES \|STANDARDS \|HISTORY \|NOTES \|SEE ALSO \|COLOPHON

mbsrtowcs(3)             Library Functions Manualmbsrtowcs(3)

NAME top

       mbsrtowcs - convert a multibyte string to a wide-character string       (restartable)

LIBRARY top

       Standard C library (libc,-lc)

SYNOPSIS top

#include <wchar.h>size_t mbsrtowcs(size_t dsize;wchar_tdest[restrictdsize],const char **restrictsrc,size_tdsize, mbstate_t *restrictps);

DESCRIPTION top

       Ifdest is not NULL, convert the multibyte string*src to a wide-       character string starting atdest.  At mostdsize wide characters       are written todest.  The shift state*ps is updated.  The       conversion is effectively performed by repeatedly callingmbrtowc(dest, *src, n, ps) wheren is some positive number, as       long as this call succeeds, and then incrementingdest by one and*src by the number of bytes consumed.  The conversion can stop for       three reasons:       •  An invalid multibyte sequence has been encountered.  In this          case,*src is left pointing to the invalid multibyte sequence,(size_t) -1 is returned, anderrno is set toEILSEQ.       •dsize non-L'\0' wide characters have been stored atdest.  In          this case,*src is left pointing to the next multibyte sequence          to be converted, and the number of wide characters written todest is returned.       •  The multibyte string has been completely converted, including          the terminating null wide character ('\0'), which has the side          effect of bringing back*ps to the initial state.  In this          case,*src is set to NULL, and the number of wide characters          written todest, excluding the terminating null wide character,          is returned.       Ifdest is NULL,dsize is ignored, and the conversion proceeds as       above, except that the converted wide characters are not written       out to memory, and that no length limit exists.       In both of the above cases, ifps is NULL, a static anonymous       state known only to thembsrtowcs() function is used instead.       In order to avoid the case 2 above, the programmer should make       suredsize is greater than or equal tombsrtowcs(NULL,src,0,ps)+1.       The programmer must ensure that there is room for at leastdsize       wide characters atdest.       This function is a restartable version ofmbstowcs(3).

RETURN VALUE top

       The number of wide characters that make up the converted part of       the wide-character string, not including the terminating null wide       character.  If an invalid multibyte sequence was encountered,(size_t) -1 is returned, anderrno set toEILSEQ.

ATTRIBUTES top

       For an explanation of the terms used in this section, seeattributes(7).       ┌─────────────┬───────────────┬──────────────────────────────────┐       │Interface│Attribute│Value│       ├─────────────┼───────────────┼──────────────────────────────────┤       │mbsrtowcs() │ Thread safety │ MT-Unsafe race:mbsrtowcs/!ps     │       └─────────────┴───────────────┴──────────────────────────────────┘

STANDARDS top

       C11, POSIX.1-2008.

HISTORY top

       POSIX.1-2001, C99.

NOTES top

       The behavior ofmbsrtowcs() depends on theLC_CTYPEcategory of       the current locale.       Passing NULL asps is not multithread safe.

COLOPHON top

       This page is part of theman-pages (Linux kernel and C library       user-space interface documentation) project.  Information about       the project can be found at        ⟨https://www.kernel.org/doc/man-pages/⟩.  If you have a bug report       for this manual page, see       ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.       This page was obtained from the tarball man-pages-6.15.tar.gz       fetched from       ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on       2025-08-11.  If you discover any rendering problems in this HTML       version of the page, or you believe there is a better or more up-       to-date source for the page, or you have corrections or       improvements to the information in this COLOPHON (which isnot       part of the original manual page), send a mail to       man-pages@man7.orgLinux man-pages 6.15            2025-06-28mbsrtowcs(3)

Pages that refer to this page:mbrtowc(3), mbsinit(3), mbsnrtowcs(3), mbstate_t(3type), mbstowcs(3), unicode(7), utf-8(7)

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