Table of Contentsisalnum, isalpha, iscntrl, isdigit, isgraph, islower, isprint, ispunct, isspace, isupper, isxdigit - character classification routines #include <ctype.h>
int isalnum (int c); int isalpha (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); 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; it is equivalent to (isupper(c) || islower(c)).
- iscntrl()
- checks for a control character.
- isdigit()
- checks for a digit.
- 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 0 a b c d e f A B C D E F
The values returned are nonzero if the character c falls into the tested class, and a zero value if not. ANSI - C, BSD 4.3 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. toupper(3), setlocale(3), ascii(7), locale(7)
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