toupper, toupper_l - transliterate lowercase characters to uppercase
int toupper(int c);
[CX] int toupper_l(int c, locale_t locale);
For toupper(): [CX] 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() [CX] 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() [CX] or toupper_l() represents a lowercase letter, and there exists a corresponding uppercase letter as defined by character type information in the current locale [CX] or in the locale represented by locale, respectively (category LC_CTYPE), the result shall be the corresponding uppercase letter.
All other arguments in the domain are returned unchanged.
[CX] 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() [CX] and toupper_l() shall return the uppercase letter corresponding to the argument passed; otherwise, they shall return the argument unchanged.
No errors are defined.
XBD Locale, <ctype.h>, <locale.h>
First released in Issue 1. Derived from Issue 1 of the SVID.
Extensions beyond the ISO C standard are marked.
SD5-XSH-ERN-181 is applied, clarifying the RETURN VALUE section.
The toupper_l() function is added from The Open Group Technical Standard, 2006, Extended API Set Part 4.
POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0673  and XSH/TC1-2008/0674  are applied.
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