TOLOWER(3) Library Functions Manual TOLOWER(3)

tolower — transliterate upper-case characters to lower-case

#include <ctype.h>

int tolower(int c);

The tolower() function has 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 behaviour is undefined. If the argument of tolower() represents an upper-case letter, and there exists a corresponding lower-case letter (as defined by character type information in the program locale category LC_CTYPE), the result is the corresponding lower-case letter. All other arguments in the domain are returned unchanged.

On successful completion, tolower() returns the lower-case letter corresponding to the argument passed; otherwise it returns the argument unchanged.

No errors are defined.

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setlocale(3) , <ctype.h> , the XBD specification, .

Derived from Issue 1 of the SVID.

February 1997 posix.fail