Manual Pages  — TOLOWER

tolower – upper case to lower case letter conversion

LIBRARY SYNOPSIS DESCRIPTION RETURN VALUES COMPATIBILITY SEE ALSO STANDARDS

Standard C Library (libc, -lc)

#include <ctype.h>

int
tolower(int c);

The tolower() function converts an upper-case letter to the corresponding lower-case letter. The argument must be representable as an unsigned char or the value of EOF.

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

The BSD 4.4 extension of accepting arguments outside of the range of the unsigned char type in locales with large character sets is considered obsolete and may not be supported in future releases. The towlower() function should be used instead.

The tolower() function conforms to ISO/IEC 9899:1990 ("ISO C90").