term% cat index.txt CTYPE(2) System Calls Manual CTYPE(2)
NAME
isalpha, isupper, islower, isdigit, isxdigit, isalnum, isspace, is‐
punct, 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(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
!"#$%&'()*+,-./:;<=>?@[\]^_`{|}~)
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 origi‐
nal character. Tolower and toupper are functions; _tolower and _toup‐
per 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.
/sys/src/libc/port/ctype.c
for the tables.
SEE ALSO
isalpharune(2)
BUGS
These macros are ASCII-centric.
CTYPE(2)