netbsd man page for ctype

CTYPE(3)						   BSD Library Functions Manual 						  CTYPE(3)

NAME
     isalpha, isupper, islower, isdigit, isxdigit, isalnum, isspace, ispunct, isprint, isgraph, iscntrl, isblank, toupper, tolower, -- character
     classification and mapping functions

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <ctype.h>

     isalpha(int c);

     isupper(int c);

     islower(int c);

     isdigit(int c);

     isxdigit(int c);

     isalnum(int c);

     isspace(int c);

     ispunct(int c);

     isprint(int c);

     isgraph(int c);

     iscntrl(int c);

     isblank(int c);

     toupper(int c);

     tolower(int c);

DESCRIPTION
     The above functions perform character tests and conversions on the integer c.

     See the specific manual pages for information about the test or conversion performed by each function.

EXAMPLES
     To print an upper-case version of a string to stdout, the following code can be used:

	   const char *s = "xyz";

	   while (*s != '') {
	       putchar(toupper((int)(unsigned char)*s));
	       s++;
	   }

SEE ALSO
     isalnum(3), isalpha(3), isblank(3), iscntrl(3), isdigit(3), isgraph(3), islower(3), isprint(3), ispunct(3), isspace(3), isupper(3),
     isxdigit(3), tolower(3), toupper(3), ascii(7)

STANDARDS
     These functions, with the exception of isblank(), conform to ANSI X3.159-1989 (``ANSI C89'').  All described functions, including isblank(),
     also conform to IEEE Std 1003.1-2001 (``POSIX.1'').

CAVEATS
     The first argument of these functions is of type int, but only a very restricted subset of values are actually valid.  The argument must
     either be the value of the macro EOF (which has a negative value), or must be a non-negative value within the range representable as unsigned
     char.  Passing invalid values leads to undefined behavior.

     Values of type int that were returned by getc(3), fgetc(3), and similar functions or macros are already in the correct range, and may be
     safely passed to these ctype functions without any casts.

     Values of type char or signed char must first be cast to unsigned char, to ensure that the values are within the correct range.  The result
     should then be cast to int to avoid warnings from some compilers.	Casting a negative-valued char or signed char directly to int will produce
     a negative-valued int, which will be outside the range of allowed values (unless it happens to be equal to EOF, but even that would not give
     the desired result).

BSD
								    May 6, 2010 							       BSD