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ctype(3) [netbsd man page]

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

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

Check Out this Related Man Page

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

isalnum, isalpha, isascii, isblank, iscntrl, isdigit, isgraph, islower, isprint, ispunct, isspace, isupper, isxdigit - character classifi- cation 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 (' '), carriage return (' '), horizontal tab (' '), 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)
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