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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.

   Alef
       These routines are not provided in Alef.

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

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

BUGS
       These macros are ASCII-centric.



                                                                      CTYPE(2)