POLL.H(7) Miscellaneous Information Manual POLL.H(7)

poll.h — definitions for the poll() function

#include <poll.h>

The <poll.h> header shall define the pollfd structure, which shall include at least the following members:

int    fd       The following descriptor being polled.
short  events   The input event flags (see below).
short  revents  The output event flags (see below).

The <poll.h> header shall define the following type through :

An unsigned integer type used for the number of file descriptors.

The implementation shall support one or more programming environments in which the width of nfds_t is no greater than the width of type . The names of these programming environments can be obtained using the confstr(3) function or the getconf(1) utility.

The <poll.h> header shall define the sigset_t type as described in <signal.h>.

The <poll.h> header shall define the structure as described in <time.h>.

The <poll.h> header shall define the following symbolic constants, zero or more of which may be OR'ed together to form the or members in the pollfd structure:

Data other than high-priority data may be read without blocking.
Normal data may be read without blocking.
Priority data may be read without blocking.
High priority data may be read without blocking.
Normal data may be written without blocking.
Equivalent to POLLOUT.
Priority data may 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.

The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided.

int   poll(struct pollfd [], nfds_t, int);
int   ppoll(struct pollfd [], nfds_t, const struct timespec *restrict,
          const sigset_t *restrict);

Inclusion of the <poll.h> header may make visible all symbols from the headers <signal.h> and <time.h>.

None.

None.

None.

XSH confstr(3), poll(3)

XCU getconf(1)

First released in Issue 4, Version 2.

The description of the symbolic constants is updated to match the poll(3) function.

Text related to STREAMS has been moved to the poll(3) reference page.

A note is added to the DESCRIPTION regarding the significance and semantics of normal, priority, and high-priority data.

The <poll.h> header is moved from the XSI option to the Base.

Austin Group Defect 1263 is applied, adding ppoll(3), requiring <poll.h> to define sigset_t and struct timespec, and allowing <poll.h> to make visible all symbols from <signal.h> and <time.h>.

June 14, 2024 posix.fail