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TOLOWER(3) Library Functions Manual TOLOWER(3)

tolower, _tolowerupper case to lower case letter conversion

#include <ctype.h>

int
tolower(int c);

int
_tolower(int c);

The () function converts an upper-case letter to the corresponding lower-case letter. The () function is identical to tolower() except that c must be an upper-case letter.

If the argument to the tolower() function is an upper-case letter, the corresponding lower-case letter is returned if there is one; otherwise the argument is returned unchanged. If the argument to the _tolower() function is an upper-case letter, the corresponding lower-case letter is returned; otherwise the output is undefined.

isalnum(3), isalpha(3), isascii(3), isblank(3), iscntrl(3), isdigit(3), isgraph(3), islower(3), isprint(3), ispunct(3), isspace(3), isupper(3), isxdigit(3), stdio(3), toascii(3), toupper(3), ascii(7)

The tolower() and _tolower() functions conform to ANSI X3.159-1989 (“ANSI C89”).

The argument to tolower must be EOF or representable as an unsigned char; otherwise, the result is undefined.

June 5, 2013 OpenBSD-5.8