CTYPE(3)

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

SYNOPSIS
#include <u.h>
#include <libc.h>
#include <ctype.h>

isalpha(c)

isupper(c)

islower(c)

isdigit(c)

isxdigit(c)

isalnum(c)

isspace(c)

ispunct(c)

isprint(c)

isgraph(c)

iscntrl(c)

isascii(c)

_toupper(c)

_tolower(c)

toupper(c)

tolower(c)

toascii(c)

DESCRIPTION
These macros classify ASCII -coded integer values by table lookup. Each is a predicate returning nonzero for true, zero for false. Isascii is defined on all integer values; the rest are defined only where isascii is true and on the single non-ASCII value EOF; see fopen(3).

isalpha
    c is a letter, a-z or A-Z

isupper
    c is an upper case letter, A-Z

islower
    c is a lower case letter, a-z

isdigit
    c is a digit, 0-9

isxdigit
    c is a hexadecimal digit, 0-9 or a-f or A-F

isalnum
    c is an alphanumeric character, a-z or A-Z or 0-9

isspace
    c is a space, horizontal tab, newline, vertical tab, formfeed, or carriage return (0x20, 0x9, 0xA, 0xB, 0xC, 0xD)

ispunct
    c is a punctuation character (one of !"#$%&'()*+,-./:;<=>?@[\]^_`{|}~)

isprint
    c is a printing character, 0x20 (space) through 0x7E (tilde)

isgraph
    c is a visible printing character, 0x21 (exclamation) through 0x7E (tilde)

iscntrl
    c is a delete character, 0x7F, or ordinary control character, 0x0 through 0x1F

isascii
    c is an ASCII character, 0x0 through 0x7F

Toascii is not a classification macro; it converts its argument to ASCII range by anding with 0x7F.

If c is an upper case letter, tolower returns the lower case version of the character; otherwise it returns the original character. Toupper is similar, returning the upper case version of a character or the original character. Tolower and toupper are functions; _tolower and _toupper are corresponding macros which should only be used when it is known that the argument is upper case or lower case, respectively.

SOURCE

/sys/include/ctype.h
    for the macros.

/usr/local/plan9/src/libc/port/ctype.c
    for the tables.

SEE ALSO
isalpharune(3)

BUGS
These macros are ASCII -centric.