CTYPE(2) CTYPE(2)
NAME
isalpha, isupper, islower, isdigit, isxdigit, isalnum,
isspace, ispunct, isprint, isgraph, iscntrl, isascii,
toascii, _toupper, _tolower, toupper, tolower - ASCII
character classification
SYNOPSIS
#include <ctype.h> isprint(c)
isalpha(c) isgraph(c)
isupper(c) iscntrl(c)
islower(c) isascii(c)
isdigit(c) _toupper(c)
isxdigit(c) _tolower(c)
isalnum(c) toupper(c)
isspace(c) tolower(c)
ispunct(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; fopen(2).
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 !"#$%&'()*+,-
./:;<=>?@[\]^_`{|}~)
Page 1 Plan 9 (printed 11/18/24)
CTYPE(2) CTYPE(2)
isprint c is a printing character, 0x20 (space) through
0x7E (tilde)
isgraph c is a visible printing character, 0x21 (exclama-
tion) 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 argu-
ment 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 corre-
sponding macros which should only be used when it is known
that the argument is upper case or lower case, respectively.
BUGS
These macros are ASCII-centric.
Page 2 Plan 9 (printed 11/18/24)