ISDIGIT(3) Library Functions Manual ISDIGIT(3)
NAME
isdigitdecimal-digit character test
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <ctype.h>
int
isdigit(int c);
DESCRIPTION
The isdigit() function tests for any decimal-digit character.
RETURN VALUES
The isdigit() function returns zero if the character tests false and returns non-zero if the character tests true.
SEE ALSO
STANDARDS
The isdigit() function conforms to ANSI X3.159-1989 (“ANSI C”).
CAVEATS
The argument to isdigit() must be EOF or representable as an unsigned char; otherwise, the behavior is undefined. See the CAVEATS section of ctype(3) for more details.