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towctrans, towctrans_l — wide-character transliteration

#include <wctype.h>
wint_t towctrans(wint_t wc, wctrans_t desc);
wint_t towctrans_l(wint_t wc, wctrans_t desc,

locale_t locale);

For towctrans(): 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 towctrans() and towctrans_l() functions shall transliterate the wide-character code wc using the mapping described by desc.

The current setting of the LC_CTYPE category in the current locale or in the locale represented by locale, respectively, should be the same as during the call to wctrans() or wctrans_l() that returned the value desc.

If the value of desc is invalid (that is, not obtained by a call to wctrans() or desc is invalidated by a subsequent call to setlocale() that has affected category LC_CTYPE), the result is unspecified.

If the value of desc is invalid (that is, not obtained by a call to wctrans_l() with the same locale object locale) the result is unspecified.

An application wishing to check for error situations should set errno to 0 before calling towctrans() or towctrans_l().

If errno is non-zero on return, an error has occurred.

The behavior is undefined if the locale argument to towctrans_l() is the special locale object LC_GLOBAL_LOCALE or is not a valid locale object handle.

If successful, the towctrans() and towctrans_l() functions shall return the mapped value of wc using the mapping described by desc. Otherwise, they shall return wc unchanged.

These functions may fail if:

desc contains an invalid transliteration descriptor.

The following sections are informative.


The strings "tolower" and "toupper" are reserved for the standard mapping names. In the table below, the functions in the left column are equivalent to the functions in the right column.

towlower(wc)            towctrans(wc, wctrans("tolower"))
towlower_l(wc, locale)  towctrans_l(wc, wctrans("tolower"), locale)
towupper(wc)            towctrans(wc, wctrans("toupper"))
towupper_l(wc, locale)  towctrans_l(wc, wctrans("toupper"), locale)



towlower(), towupper(), wctrans()

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

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 .

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 .

2017 IEEE/The Open Group