diff options
Diffstat (limited to 'lib/libc/sys/poll.2')
| -rw-r--r-- | lib/libc/sys/poll.2 | 47 |
1 files changed, 31 insertions, 16 deletions
diff --git a/lib/libc/sys/poll.2 b/lib/libc/sys/poll.2 index 3456350..28c426e 100644 --- a/lib/libc/sys/poll.2 +++ b/lib/libc/sys/poll.2 @@ -50,7 +50,8 @@ The .Fa fds argument is a pointer to an array of pollfd structures as defined in .In poll.h -(shown below). The +(shown below). +The .Fa nfds argument determines the size of the .Fa fds @@ -68,13 +69,16 @@ The fields of are as follows: .Bl -tag -width XXXrevents .It fd -File descriptor to poll. If fd is equal to -1 then +File descriptor to poll. +If fd is equal to -1 then .Fa revents is cleared (set to zero), and that pollfd is not checked. .It events -Events to poll for. (See below.) +Events to poll for. +(See below.) .It revents -Events which may occur. (See below.) +Events which may occur. +(See below.) .El .Pp The event bitmasks in @@ -97,15 +101,18 @@ Normal data may be written without blocking. .It POLLWRBAND Data with a non-zero priority may be written without blocking. .It POLLERR -An exceptional condition has occurred on the device or socket. This +An exceptional condition has occurred on the device or socket. +This flag is always checked, even if not present in the .Fa events bitmask. .It POLLHUP -The device or socket has been disconnected. This flag is always +The device or socket has been disconnected. +This flag is always checked, even if not present in the .Fa events -bitmask. Note that +bitmask. +Note that POLLHUP and POLLOUT @@ -113,7 +120,8 @@ should never be present in the .Fa revents bitmask at the same time. .It POLLNVAL -The file descriptor is not open. This flag is always checked, even +The file descriptor is not open. +This flag is always checked, even if not present in the .Fa events bitmask. @@ -122,9 +130,11 @@ bitmask. If .Fa timeout is neither zero nor INFTIM (-1), it specifies a maximum interval to -wait for any file descriptor to become ready, in milliseconds. If +wait for any file descriptor to become ready, in milliseconds. +If .Fa timeout -is INFTIM (-1), the poll blocks indefinitely. If +is INFTIM (-1), the poll blocks indefinitely. +If .Fa timeout is zero, then .Fn poll @@ -134,7 +144,8 @@ The .Fn poll system call returns the number of descriptors that are ready for I/O, or -1 if an -error occurred. If the time limit expires, +error occurred. +If the time limit expires, .Fn poll returns 0. If @@ -148,15 +159,18 @@ array will be unmodified. This implementation differs from the historical one in that a given file descriptor may not cause .Fn poll -to return with an error. In cases where this would have happened in -the historical implementation (e.g. trying to poll a +to return with an error. +In cases where this would have happened in +the historical implementation (e.g.\& trying to poll a .Xr revoke 2 Ns ed descriptor), this implementation instead copies the .Fa events bitmask to the .Fa revents -bitmask. Attempting to perform I/O on this descriptor will then -return an error. This behaviour is believed to be more useful. +bitmask. +Attempting to perform I/O on this descriptor will then +return an error. +This behaviour is believed to be more useful. .Sh ERRORS An error return from .Fn poll @@ -187,7 +201,8 @@ The distinction between some of the fields in the .Fa events and .Fa revents -bitmasks is really not useful without STREAMS. The fields are +bitmasks is really not useful without STREAMS. +The fields are defined for compatibility with existing software. .Sh HISTORY The |
