CTYPE(3)

NAME
ctype, isalpha, isupper, islower, isdigit, isxdigit, isalnum, isspace, ispunct, isprint, isgraph, iscntrl, isascii, toupper, tolower, toascii - character classification macros

SYNOPSIS
#include <ctype.h>
int isalpha(int c)
...

DESCRIPTION
These macros classify characters by table lookup. Each is a predicate returning nonzero for true, zero for false. Isascii and toascii are defined on all integer values; the rest are defined only on the range of unsigned char and on the special value EOF (see stdio(3)).

isalpha
    c is a letter

isupper
    c is an upper case letter

islower
    c is a lower case letter

isdigit
    c is a digit

isxdigit
    c is a hex digit

isalnum
    c is an alphanumeric character

isspace
    c is a space, tab, carriage return, newline, vertical tab, or formfeed

ispunct
    c is a punctuation character (neither control nor alphanumeric)

isprint
    c is a printing character, code 040(8) (space) through 0176 (tilde)

isgraph
    c is a printing character, similar to isprint except false for space.

iscntrl
    c is a delete character (0177) or ordinary control character (less than 040).

isascii
    c is an ASCII character, code less than 0200

tolower
    c is converted to lower case. Return value is undefined if not isupper(c).

toupper
    c is converted to upper case. Return value is undefined if not islower(c).

toascii
    c is converted to be a valid ascii character.

SEE ALSO
ascii(7)