ISALPHA(3)          Linux Programmer's Manual          ISALPHA(3)

NAME
       isalnum,  isalpha,  isascii,  isblank,  iscntrl,  isdigit,
       isgraph,  islower,  isprint,  ispunct,  isspace,  isupper,
       isxdigit - character classification routines

SYNOPSIS
       #include <ctype.h>

       int isalnum (int c);
       int isalpha (int c);
       int isascii (int c);
       int isblank (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);

DESCRIPTION
       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 current locale.

       isalnum()
              checks for an alphanumeric character; it is equiva-
              lent to (isalpha(c) || isdigit(c)).

       isalpha()
              checks for an alphabetic character; in the standard
              "C"  locale,  it  is  equivalent  to (isupper(c) ||
              islower(c)).  In some locales, there may  be  addi-
              tional characters for which isalpha() is true--let-
              ters which are neither upper case nor lower case.

       isascii()
              checks whether c is a  7-bit  unsigned  char  value
              that fits into the ASCII character set.  This func-
              tion is a BSD extension and is also an SVID  exten-
              sion.

       isblank()
              checks for a blank character; that is, a space or a
              tab.  This function is a GNU extension.

       iscntrl()
              checks for a control character.

       isdigit()
              checks for a digit (0 through 9).

       isgraph()
              checks for any printable character except space.

       islower()
              checks for a lower-case character.

       isprint()
              checks for any printable character including space.

       ispunct()
              checks  for  any printable character which is not a
              space or an alphanumeric character.

       isspace()
              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').

       isupper()
              checks for an uppercase letter.

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

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

CONFORMING TO
       ANSI  -  C,  BSD 4.3.  isascii() is a BSD extension and is
       also an SVID extension.  isblank() is a GNU extension.

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

SEE ALSO
       tolower(3), toupper(3), setlocale(3), ascii(7), locale(7)

GNU                     September 2, 1995                       1