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       isalnum,  isalpha, isascii, isblank, iscntrl, isdigit, isgraph, islower, isprint, ispunct,
       isspace,  isupper,  isxdigit,  isalnum_l,  isalpha_l,  isascii_l,  isblank_l,   iscntrl_l,
       isdigit_l,  isgraph_l, islower_l, isprint_l, ispunct_l, isspace_l, isupper_l, isxdigit_l -
       character classification functions


       Standard C library (libc, -lc)


       #include <ctype.h>

       int isalnum(int c);
       int isalpha(int c);
       int iscntrl(int c);
       int isdigit(int c);
       int isgraph(int c);
       int islower(int c);
       int isprint(int c);
       int ispunct(int c);
       int isspace(int c);
       int isupper(int c);
       int isxdigit(int c);

       int isascii(int c);
       int isblank(int c);

       int isalnum_l(int c, locale_t locale);
       int isalpha_l(int c, locale_t locale);
       int isblank_l(int c, locale_t locale);
       int iscntrl_l(int c, locale_t locale);
       int isdigit_l(int c, locale_t locale);
       int isgraph_l(int c, locale_t locale);
       int islower_l(int c, locale_t locale);
       int isprint_l(int c, locale_t locale);
       int ispunct_l(int c, locale_t locale);
       int isspace_l(int c, locale_t locale);
       int isupper_l(int c, locale_t locale);
       int isxdigit_l(int c, locale_t locale);

       int isascii_l(int c, locale_t locale);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

               || /* glibc >= 2.19: */ _DEFAULT_SOURCE
               || /* glibc <= 2.19: */ _SVID_SOURCE

           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L

       isalnum_l(), isalpha_l(), isblank_l(), iscntrl_l(), isdigit_l(), isgraph_l(), islower_l(),
       isprint_l(), ispunct_l(), isspace_l(), isupper_l(), isxdigit_l():
           Since glibc 2.10:
               _XOPEN_SOURCE >= 700
           Before glibc 2.10:

           Since glibc 2.10:
               _XOPEN_SOURCE >= 700 && (_SVID_SOURCE || _BSD_SOURCE)
           Before glibc 2.10:


       These  functions  check  whether  c, which must have the value of an unsigned char or EOF,
       falls into a certain character class according to the  specified  locale.   The  functions
       without the "_l" suffix perform the check based on the current locale.

       The  functions with the "_l" suffix perform the check based on the locale specified by the
       locale object locale.  The behavior of these functions  is  undefined  if  locale  is  the
       special  locale object LC_GLOBAL_LOCALE (see duplocale(3)) or is not a valid locale object

       The list below explains the operation of  the  functions  without  the  "_l"  suffix;  the
       functions  with  the  "_l" suffix differ only in using the locale object locale instead of
       the current locale.

              checks  for  an  alphanumeric  character;  it  is  equivalent  to  (isalpha(c)   ||

              checks for an alphabetic character; in the standard "C" locale, it is equivalent to
              (isupper(c) || islower(c)).  In some locales, there may  be  additional  characters
              for which isalpha() is true—letters which are neither uppercase nor lowercase.

              checks  whether c is a 7-bit unsigned char value that fits into the ASCII character

              checks for a blank character; that is, a space or a tab.

              checks for a control character.

              checks for a digit (0 through 9).

              checks for any printable character except space.

              checks for a lowercase character.

              checks for any printable character including space.

              checks for any printable  character  which  is  not  a  space  or  an  alphanumeric

              checks  for  white-space  characters.   In  the "C" and "POSIX" locales, these are:
              space, form-feed ('\f'), newline ('\n'), carriage  return  ('\r'),  horizontal  tab
              ('\t'), and vertical tab ('\v').

              checks for an uppercase letter.

              checks for hexadecimal digits, that is, one of
              0 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F.


       The  values  returned are nonzero if the character c falls into the tested class, and zero
       if not.


       isalnum_l(), isalpha_l(), isblank_l(), iscntrl_l(), isdigit_l(), isgraph_l(), islower_l(),
       isprint_l(),  ispunct_l(),  isspace_l(),  isupper_l(),  isxdigit_l(),  and isascii_l() are
       available since glibc 2.3.


       For an explanation of the terms used in this section, see attributes(7).

       │InterfaceAttributeValue   │
       │isalnum(), isalpha(), isascii(), isblank(), iscntrl(),         │ Thread safety │ MT-Safe │
       │isdigit(), isgraph(), islower(), isprint(), ispunct(),         │               │         │
       │isspace(), isupper(), isxdigit()                               │               │         │


       POSIX.1-2001 specifies isalnum(), isalpha(), isblank(), iscntrl(),  isdigit(),  isgraph(),
       islower(),  isprint(), ispunct(), isspace(), isupper(), and isxdigit(), and also isascii()
       (as an XSI extension).  C99 specifies all of the preceding functions, except isascii().

       POSIX.1-2008 marks isascii() as obsolete, noting that it cannot  be  used  portably  in  a
       localized application.

       POSIX.1-2008  specifies  isalnum_l(),  isalpha_l(), isblank_l(), iscntrl_l(), isdigit_l(),
       isgraph_l(),  islower_l(),  isprint_l(),  ispunct_l(),   isspace_l(),   isupper_l(),   and

       isascii_l() is a GNU extension.


       The  standards  require  that  the argument c for these functions is either EOF or a value
       that is representable in the type unsigned char.  If the argument c is of  type  char,  it
       must be cast to unsigned char, as in the following example:

           char c;
           res = toupper((unsigned char) c);

       This  is necessary because char may be the equivalent of signed char, in which case a byte
       where the top bit is set would be sign extended when converting to int, yielding  a  value
       that is outside the range of unsigned char.

       The  details  of what characters belong to which class depend on the locale.  For example,
       isupper() will not recognize an A-umlaut (Ä) as an  uppercase  letter  in  the  default  C


       iswalnum(3), iswalpha(3), iswblank(3), iswcntrl(3), iswdigit(3), iswgraph(3), iswlower(3),
       iswprint(3),   iswpunct(3),   iswspace(3),   iswupper(3),   iswxdigit(3),    newlocale(3),
       setlocale(3), toascii(3), tolower(3), toupper(3), uselocale(3), ascii(7), locale(7)