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ISDIGIT(3) Library Functions Manual ISDIGIT(3)

isdigitdecimal-digit character test

#include <ctype.h>

isdigit(int c);

The () function tests for any decimal-digit character.

The isdigit() function returns zero if the character tests false or non-zero if the character tests true.

isalnum(3), isalpha(3), isascii(3), isblank(3), iscntrl(3), isgraph(3), islower(3), isprint(3), ispunct(3), isspace(3), isupper(3), isxdigit(3), stdio(3), toascii(3), tolower(3), toupper(3), ascii(7)

The isdigit() function conforms to ANSI X3.159-1989 (“ANSI C89”).

The isdigit() function first appeared in Version 7 AT&T UNIX.

The argument to isdigit() must be EOF or representable as an unsigned char; otherwise, the result is undefined.

July 17, 2013 OpenBSD-6.1