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


   #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 since 2.19: */ _DEFAULT_SOURCE
           || /* Glibc versions <= 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) || isdigit(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 set.

          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 character.

          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

          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


   For   an   explanation   of   the  terms  used  in  this  section,  see

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


   C89 specifies isalnum(), isalpha(),  iscntrl(),  isdigit(),  isgraph(),
   islower(),  isprint(), ispunct(), isspace(), isupper(), and isxdigit(),
   but not isascii() and isblank().   POSIX.1-2001  also  specifies  those
   functions, and also isascii() (as an XSI extension) and isblank().  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 isxdigit_l().

   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 locale.


   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)


   This page is part of release 4.09 of the Linux  man-pages  project.   A
   description  of  the project, information about reporting bugs, and the
   latest    version    of    this    page,    can     be     found     at

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