X-Git-Url: https://git.saurik.com/apple/xnu.git/blobdiff_plain/55e303ae13a4cf49d70f2294092726f2fffb9ef2..f427ee49d309d8fc33ebf3042c3a775f2f530ded:/bsd/man/man2/select.2 diff --git a/bsd/man/man2/select.2 b/bsd/man/man2/select.2 index 39fd5d84b..b6b56c034 100644 --- a/bsd/man/man2/select.2 +++ b/bsd/man/man2/select.2 @@ -33,31 +33,59 @@ .\" .\" @(#)select.2 8.2 (Berkeley) 3/25/94 .\" -.Dd March 25, 1994 +.Dd March 18, 2015 .Dt SELECT 2 .Os BSD 4.2 .Sh NAME +.Nm FD_CLR , +.Nm FD_COPY , +.Nm FD_ISSET , +.Nm FD_SET , +.Nm FD_ZERO , .Nm select .Nd synchronous I/O multiplexing .Sh SYNOPSIS .Fd #include -.D1 "- or -" -.Fd #include -.Fd #include -.Fd #include +.\" +.Ft void +.Fo FD_CLR +.Fa fd +.Fa "fd_set *fdset" +.Fc +.Ft void +.Fo FD_COPY +.Fa "fd_set *fdset_orig" +.Fa "fd_set *fdset_copy" +.Fc .Ft int -.Fn select "int nfds" "fd_set *readfds" "fd_set *writefds" "fd_set *exceptfds" "struct timeval *timeout" -.Fn FD_SET fd &fdset -.Fn FD_CLR fd &fdset -.Fn FD_ISSET fd &fdset -.Fn FD_ZERO &fdset +.Fo FD_ISSET +.Fa fd +.Fa "fd_set *fdset" +.Fc +.Ft void +.Fo FD_SET +.Fa fd +.Fa "fd_set *fdset" +.Fc +.Ft void +.Fo FD_ZERO +.Fa "fd_set *fdset" +.Fc +.Ft int +.Fo select +.Fa "int nfds" +.Fa "fd_set *restrict readfds" +.Fa "fd_set *restrict writefds" +.Fa "fd_set *restrict errorfds" +.Fa "struct timeval *restrict timeout" +.Fc .Sh DESCRIPTION -.Fn Select +.Fn select examines the I/O descriptor sets whose addresses are passed in .Fa readfds , .Fa writefds , and -.Fa exceptfds +.Fa errorfds to see if some of their descriptors are ready for reading, are ready for writing, or have an exceptional condition pending, respectively. @@ -66,13 +94,15 @@ The first descriptors are checked in each set; i.e., the descriptors from 0 through .Fa nfds Ns No -1 -in the descriptor sets are examined. +in the descriptor sets are examined. (Example: If you have set two file descriptors "4" and "17", +.Fa nfds +should not be "2", but rather "17 + 1" or "18".) On return, .Fn select replaces the given descriptor sets with subsets consisting of those descriptors that are ready for the requested operation. -.Fn Select +.Fn select returns the total number of ready descriptors in all the sets. .Pp The descriptor sets are stored as bit fields in arrays of integers. @@ -97,6 +127,11 @@ is non-zero if is a member of .Fa fdset , zero otherwise. +.Fn FD_COPY &fdset_orig &fdset_copy +replaces an already allocated +.Fa &fdset_copy +file descriptor set with a copy of +.Fa &fdset_orig . The behavior of these macros is undefined if a descriptor value is less than zero or greater than or equal to .Dv FD_SETSIZE , @@ -105,13 +140,19 @@ to the maximum number of descriptors supported by the system. .Pp If .Fa timeout -is a non-nil pointer, it specifies a maximum interval to wait for the -selection to complete. If +is not a null pointer, it specifies a maximum interval to wait for the +selection to complete. +.Pp +If +.Fa timeout +is a null pointer, the select blocks indefinitely. +.Pp +To effect a poll, the .Fa timeout -is a nil pointer, the select blocks indefinitely. To effect a poll, the +argument should be not be a null pointer, +but it should point to a zero-valued timeval structure. +.Pp .Fa timeout -argument should be non-nil, pointing to a zero-valued timeval structure. -.Fa Timeout is not changed by .Fn select , and may be reused on subsequent calls, however it is good style to re-initialize @@ -122,10 +163,10 @@ Any of .Fa readfds , .Fa writefds , and -.Fa exceptfds -may be given as nil pointers if no descriptors are of interest. +.Fa errorfds +may be given as null pointers if no descriptors are of interest. .Sh RETURN VALUES -.Fn Select +.Fn select returns the number of ready descriptors that are contained in the descriptor sets, or -1 if an error occurred. @@ -136,30 +177,85 @@ If .Fn select returns with an error, including one due to an interrupted call, -the descriptor sets will be unmodified. +the descriptor sets will be unmodified and the global variable +.Va errno +will be set to indicate the error. .Sh ERRORS An error return from .Fn select indicates: .Bl -tag -width Er +.\" =========== +.It Bq Er EAGAIN +The kernel was (perhaps temporarily) unable +to allocate the requested number of file descriptors. +.\" =========== .It Bq Er EBADF One of the descriptor sets specified an invalid descriptor. +.\" =========== .It Bq Er EINTR A signal was delivered before the time limit expired and before any of the selected events occurred. +.\" =========== .It Bq Er EINVAL The specified time limit is invalid. One of its components is negative or too large. +.\" =========== +.It Bq Er EINVAL +.Fa ndfs +is greater than FD_SETSIZE and _DARWIN_UNLIMITED_SELECT is not defined. .El +.Sh LEGACY SYNOPSIS +.Fd #include +.D1 "- or -" +.Fd #include +.Fd #include +.Fd #include +.Pp +.Fo FD_SET +.Fa fd +.Fa &fdset +.Fc ; +.Pp +.Fo FD_CLR +.Fa fd +.Fa &fdset +.Fc ; +.Pp +.Fo FD_ISSET +.Fa fd +.Fa &fdset +.Fc ; +.Pp +.Fo FD_COPY +.Fa &fdset_orig +.Fa &fdset_copy +.Fc ; +.Pp +.Fo FD_ZERO +.Fa &fdset +.Fc ; +.Sh COMPATIBILITY +.Fn select +now returns with +.Va errno +set to EINVAL when +.Fa nfds +is greater than FD_SETSIZE. +Use a smaller value for +.Fa nfds +or compile with -D_DARWIN_UNLIMITED_SELECT. .Sh SEE ALSO .Xr accept 2 , .Xr connect 2 , +.Xr connectx 2 , .Xr getdtablesize 2 , .Xr gettimeofday 2 , .Xr read 2 , .Xr recv 2 , .Xr send 2 , -.Xr write 2 +.Xr write 2 , +.Xr compat 5 .Sh BUGS Although the provision of .Xr getdtablesize 2 @@ -178,7 +274,7 @@ a larger definition of before the inclusion of .Aq Pa sys/types.h . .Pp -.Fn Select +.Fn select should probably have been designed to return the time remaining from the original timeout, if any, by modifying the time value in place. However, it is unlikely this semantic will ever be implemented, as the