toupper, tolower, _toupper, _tolower, toascii - translate characters
The functions and have as their domain the range of the function. If
the argument to represents a lowercase letter, the output from the
function is the corresponding uppercase letter. If the argument to rep‐
resents an uppercase letter, the result is the corresponding lowercase
The case of c depends on the definition of the character in the lan‐
guage database. Because the case of a character can vary between lan‐
guage databases, the case of c depends on what language database is in
use. Specifically, the case of arguments depends on what property
tables are associated the LC_CTYPE category. Property tables are asso‐
ciated with the LC_CTYPE category by a successful call to the function
that includes the LC_CTYPE category. If no successful call to define
LC_CTYPE has occurred or if the character case information is unavail‐
able for the language in use, the rules of the ASCII coded character
set determine the case of arguments.
If the argument to the function does not have the uppercase attribute,
returns the argument unchanged. Likewise, if the argument to the func‐
tion does not have the lowercase attribute, returns it unchanged.
The macros and have the same affect as and The difference is that the
argument to the macros must be an ASCII character (that is, a character
in the domain -1 to 127) and the argument must have the appropriate
case. Arguments to must have the uppercase attribute and arguments to
must the lowercase attribute. The result of supplying arguments to
these macros that are outside the domain or do not have the appropriate
case is undefined. These macros operate faster than the and functions.
The macro converts its argument to the ASCII character set. The macro
converts its argument by truncating the numerical representation of the
argument so that it is between -1 and 127. You can use this macro when
you move an application to a system other than an ULTRIX system.
LC_CTYPE If this environment variable is set and valid, uses the
international language database named in the definition
to determine character classification rules.
See Alsoctype(3int), setlocale(3), getc(3)conv(3)