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nfds should be prototyped as nfds_t; as per Debian bug 322934 

Some wording and formatting improvements.
This commit is contained in:
Michael Kerrisk 2005-08-16 08:46:16 +00:00
parent 7dfefab847
commit 96296ef0fa
1 changed files with 25 additions and 18 deletions
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43
man2/poll.2
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@ -30,21 +30,23 @@ poll \- wait for some event on a file descriptor
.SH SYNOPSIS
.B #include <sys/poll.h>
.sp
.BI "int poll(struct pollfd *" ufds ", unsigned int " nfds ", int " timeout );
.BI "int poll(struct pollfd *" ufds ", nfds_t " nfds ", int " timeout );
.SH DESCRIPTION
.B poll
.BR poll ()
is a variation on the theme of
.BR select .
.BR select ().
It specifies an array of
.I nfds
structures of type
.br
.nf
struct pollfd {
int fd; /* file descriptor */
short events; /* requested events */
short revents; /* returned events */
};
struct pollfd {
int fd; /* file descriptor */
short events; /* requested events */
short revents; /* returned events */
};
.fi
and a
.I timeout
@ -75,40 +77,45 @@ If none of the events requested (and no error) has occurred for any
of the file descriptors, the kernel waits for
.I timeout
milliseconds for one of these events to occur.
The following possible bits in these masks are defined in <sys/poll.h>
The following possible bits in these masks are defined in <sys/poll.h>:
.br
.nf
#define POLLIN 0x0001 /* There is data to read */
#define POLLPRI 0x0002 /* There is urgent data to read */
#define POLLOUT 0x0004 /* Writing now will not block */
#define POLLERR 0x0008 /* Error condition */
#define POLLHUP 0x0010 /* Hung up */
#define POLLNVAL 0x0020 /* Invalid request: fd not open */
.fi
When compiling XPG4.2 source one also has
When compiling XPG4.2 source one also has:
.br
.nf
#ifdef _XOPEN_SOURCE
#ifdef _XOPEN_SOURCE
#define POLLRDNORM 0x0040 /* Normal data may be read */
#define POLLRDBAND 0x0080 /* Priority data may be read */
#define POLLWRNORM 0x0100 /* Writing now will not block */
#define POLLWRBAND 0x0200 /* Priority data may be written */
#endif
#endif
.fi
Finally, Linux knows about
Finally, Linux knows about:
.br
.nf
#ifdef _GNU_SOURCE
#ifdef _GNU_SOURCE
#define POLLMSG 0x0400
#endif
#endif
.fi
.SH "RETURN VALUE"
On success, a positive number is returned, where the number returned
is the number of structures which have non-zero
On success, a positive number is returned; this is
the number of structures which have non-zero
.I revents
fields (in other words, those descriptors with events or errors reported).
A value of 0 indicates that the call timed out and no file
descriptors have been selected. On error, \-1 is returned, and
descriptors were ready. On error, \-1 is returned, and
.I errno
is set appropriately.
.SH ERRORS