Indicates if a specified file descriptor is associated with a
    pipe.

    Format

      #include  <unixio.h>

      int isapipe  (int file_desc);

1 - Argument

 file_desc

    A file descriptor.

2 - Description

    For more information about pipes, see the "Subprocess Functions"
    chapter of the HP C RTL Reference Manual.

3 - Return Values

    1                  Indicates an association with a pipe.
    0                  Indicates no association with a pipe.
    -1                 Indicates an error (for example, if the file
                       descriptor is not associated with an open
                       file).