isdigit

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 equivalent 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 additional characters for which isalpha()
	      is true--letters 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 function is a BSD extension  and
	      is also an SVID extension.

       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				  1995-09-02			   ISALPHA(3)