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 (isal-
              pha(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.


       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)