isastream(3C)                  DG/UX R4.11MU05                 isastream(3C)


NAME
       isastream - test a file descriptor

SYNOPSIS
       int isastream(int fildes);

DESCRIPTION
       The function isastream() determines if a file descriptor represents a
       STREAMS file.  fildes refers to an open file.


   Considerations for Threads Programming
                     +----------+-----------------------------+
                     |          |                      async- |
                     |function  | reentrant   cancel   cancel |
                     |          |             point     safe  |
                     +----------+-----------------------------+
                     |isastream |     Y         Y        N    |
                     +----------+-----------------------------+

RETURN VALUE
       If successful, isastream() returns 1 if fildes represents a STREAMS
       file, and 0 if not.  On failure, isastream() returns -1 with errno
       set to indicate an error.

DIAGNOSTICS
       Under the following conditions, isastream() fails and sets errno to:

       EBADF        fildes is not a valid open file.

SEE ALSO
       reentrant(3) and streamio(7)
       in the Programmer's Guide: STREAMS


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