isprint(3) - Linux man page

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.
isblank(): checks for a blank character; that is, a space or a tab.
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 non-zero if the character c falls into the tested class, and a zero value if not.

Conforming to

C99, 4.3BSD. isascii() is a BSD extension and is also an SVr4 extension. isblank() conforms to POSIX.1-2001 and C99 7.4.1.3.

Note

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

Referenced By

h_read(1), lsof(8)