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(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 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. 

­/sys/src/libc/port/ctype.c
for the tables.

SEE ALSO

isalpharune(2)

BUGS

These macros are ASCII -centric. 

Plan 9  —  March 17, 2004