conv(3)conv(3)NAME
toascii, tolower, _tolower, toupper, _toupper - Translate characters
SYNOPSIS
#include <ctype.h>
int toascii(
int c ); int tolower(
int c ); int _tolower(
int c ); int toupper(
int c ); int _toupper(
int c );
LIBRARY
Standard C Library (libc)
STANDARDS
Interfaces documented on this reference page conform to industry stan‐
dards as follows:
toascii(), tolower(), _tolower(), toupper(), _toupper(): XPG4,
XPG4-UNIX
Refer to the standards(5) reference page for more information about
industry standards and associated tags.
PARAMETERS
Specifies the character to be converted.
DESCRIPTION
The toascii(), tolower(), _tolower(), toupper(), and _toupper() func‐
tions translate all characters, including multibyte characters, to
their specified character values.
The toascii() function converts its input to a 7-bit ASCII character.
The tolower() function takes an int value that can be represented as an
unsigned char or the value of EOF (defined in the stdio.h header file)
as its input.
When the input of the tolower() function expresses an uppercase letter,
and there exists a corresponding lowercase letter (as defined by char‐
acter type information in the program locale category LC_CTYPE), the
corresponding lowercase letter is returned. All other input values in
the domain are returned unchanged. The tolower() function has as its
domain the range -1 through 255.
In the C locale, or in a locale where case-conversion information is
not defined, the tolower() function determines the case of characters
according to the rules of the Portable Character Set (ASCII charac‐
ters). Characters outside the ASCII range of characters are returned
unchanged.
The _tolower() macro is equivalent to the tolower() function, but exe‐
cutes faster. If the value of the c parameter to the _tolower() macro
does not have a corresponding lowercase character, the results of the
function are undefined.
The toupper() function takes an int value that can be represented as an
unsigned char or the value of EOF (defined in the stdio.h header file)
as its input.
When the input of the toupper() function expresses a lowercase letter,
and there exists a corresponding uppercase letter (as defined by char‐
acter type information in the program locale category LC_CTYPE), the
corresponding uppercase letter is returned. All other input values in
the domain are returned unchanged. The toupper() function has as its
domain the range -1 through 255.
In the C locale, or in a locale where case-conversion information is
not defined, the toupper() function determines the case of characters
according to the rules of the Portable Character Set (ASCII charac‐
ters). Characters outside the ASCII range of characters are returned
unchanged.
The _toupper() macro is equivalent to the toupper() function, but exe‐
cutes faster. If the value of the c parameter to the _toupper() macro
does not have a corresponding uppercase character, the results of the
function are undefined.
NOTES
The LC_CTYPE category of the current locale affects all conversions.
See the i18n_intro(5) reference page for more information on locale
variables.
RETURN VALUES
The toascii() function returns the logical AND of parameter c and the
value 0X7F.
When the c parameter is a character for which the isupper() function is
TRUE, there is a corresponding character for which the islower() func‐
tion is also TRUE. That lowercase character is returned by the
tolower() function or by the _tolower() macro. Otherwise, the c parame‐
ter is returned unchanged.
When the c parameter is a character for which the islower() function is
TRUE, there is a corresponding character for which the isupper() func‐
tion is also TRUE. That uppercase character is returned by the toup‐
per() function or by the _toupper() macro. Otherwise, the c parameter
is returned unchanged.
SEE ALSO
Functions: ctype(3)
Other: i18n_intro(5), standards(5)conv(3)