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.
toupper, toupper_l — transliterate lowercase characters to uppercase
int toupper(int c);
int toupper_l(int c, locale_t locale);
For toupper(): 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 toupper() and toupper_l() functions have as a
domain a type int, the value of which is representable as an
unsigned char or the value of EOF. If the argument has any other
value, the behavior is undefined.
If the argument of toupper() or toupper_l()
represents a lowercase letter, and there exists a corresponding uppercase
letter as defined by character type information in the current locale or in
the locale represented by locale, respectively (category
LC_CTYPE), the result shall be the corresponding uppercase
All other arguments in the domain are returned unchanged.
The behavior is undefined if the locale argument to
toupper_l() is the special locale object LC_GLOBAL_LOCALE or is not a
valid locale object handle.
Upon successful completion, toupper() and toupper_l() shall return
the uppercase letter corresponding to the argument passed; otherwise, they
shall return the argument unchanged.
No errors are defined.
The following sections are informative.
The Base Definitions volume of POSIX.1‐2017, Chapter
7, Locale, <ctype.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 http://www.opengroup.org/unix/online.html .
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