The <poll.h> header defines the pollfd structure, which includes the following members:
the following descriptor being polled
the input event flags (see below)
the output event flags (see below)
The <poll.h> header defines the following type through typedef:
an unsigned integer type used for the number of file descriptors
The implementation supports one or more programming environments in which the width of nfds_t is no greater than the width of type long. The names of these programming environments can be obtained using the confstr() function or the getconf utility. See confstr(3C) and getconf( 1).
The following symbolic constants are defined, zero or more of which can be OR'ed together to form the events or revents members in the pollfd structure:
Data other than high-priority data can be read without blocking.
Normal data can be read without blocking.
Priority data can be read without blocking.
High priority data can be read without blocking.
Normal data can be written without blocking.
Equivalent to POLLOUT.
Priority data can be written.
An error has occurred (revents only).
Device has been disconnected (revents only).
Invalid fd member (revents only).
The significance and semantics of normal, priority, and high-priority data are file and device-specific.
See attributes(5) for descriptions of the following attributes: