TOUPPERSection: Linux Programmer's Manual (3)
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NAMEtoupper, tolower - convert letter to upper or lower case
#include <ctype.h> int toupper(int c);
int tolower(int c);
DESCRIPTIONtoupper() converts the letter c to upper case, if possible.
tolower() converts the letter c to lower case, if possible.
RETURN VALUEThe value returned is that of the converted letter, or c if the conversion was not possible.
CONFORMING TOC89, C99, 4.3BSD.
BUGSThe details of what constitutes an uppercase or lowercase letter depend on the current locale. For example, the default C locale does not know about umlauts, so no conversion is done for them.
SEE ALSOisalpha(3), setlocale(3), towlower(3), towupper(3), locale(7)
COLOPHONThis page is part of release 3.21 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.