is...()

Function

Check whether a character falls into a given category.

Syntax

int isalnum(char c);
int isalpha(char c);
int iscntrl(char c);
int isdigit(char c);
int isgraph(char c);
int islower(char c);
int isprint(char c);
int ispunct(char c);
int isspace(char c);
int isupper(char c);
int isxdigit(char c);

Returns

The is... functions return nonzero if the given character falls into the category, zero otherwise.

isalnum	letters (A to Z or a to z) or digits (0 to 9)
isalpha	letters (A to Z or a to z)
iscntrl	delete characters or ordinary control characters (0x7F or 0x00 to 0x1F)
isdigit	digits (0 to 9)
isgraph	printing characters (except space)
islower	lowercase letters (a to z)
isprint	printing characters (0x20 to 0x7E)
ispunct	punctuation characters (iscntrl or isspace)
isspace	space, tab, carriage return, new line, vertical tab, or formfeed (0x09 to 0x0D, 0x20)
isupper	uppercase letters (A to Z)
isxdigit	hex digits (0 to 9, A to F, a to f)

Example

char c = 'A';
if (isxdigit(c))
   printf("%c is hex\n", c);
else
   printf("%c is not hex\n", c);