isastream - test file descriptor

Syntax	#include <stropts.h> int isastream(int fildes);
Description	The isastream() function checks whether a file descriptor represents a STREAMS file. fildes refers to an open file.
Return val.	1 0 -1	if fildes represents a STREAMS file. if fildes does not represent a STREAMS file. if an error occurs. errno is set to indicate the error.
Errors	isastream() will fail if: EBADF            fildes is not a valid open file descriptor.
See also	stropts.h.