isalnum, isalnum_l—alphanumeric character predicateSynopsis
#include <ctype.h> int isalnum(int c); #include <ctype.h> int isalnum_l(int c, locale_t locale);
Description
isalnum is a macro which classifies singlebyte charset values by table
lookup. It is a predicate returning non-zero for alphabetic or
numeric ASCII characters, and 0 for other arguments. It is defined
only if c is representable as an unsigned char or if c is EOF.
isalnum_l is like isalnum but performs the check based on the
locale specified by the locale object locale. If locale is
LC_GLOBAL_LOCALE or not a valid locale object, the behaviour is undefined.
You can use a compiled subroutine instead of the macro definition by
undefining the macro using ‘#undef isalnum’ or ‘#undef isalnum_l’.
Returns
isalnum,isalnum_l return non-zero if c is a letter or a digit.
Portability
isalnum is ANSI C.
isalnum_l is POSIX-1.2008.
No OS subroutines are required.