mirror of https://github.com/mkerrisk/man-pages
164 lines
4.3 KiB
Groff
164 lines
4.3 KiB
Groff
.\" Copyright (c) 2002 Michael kerrisk <mtk.manpages@gmail.com>
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\"
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.TH SIGWAITINFO 2 2007-07-26 "Linux" "Linux Programmer's Manual"
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.SH NAME
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sigwaitinfo, sigtimedwait \- synchronously wait for queued signals
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.SH SYNOPSIS
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.nf
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.B #include <signal.h>
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.sp
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.BI "int sigwaitinfo(const sigset_t *" set ", siginfo_t *" info ");"
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.sp
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.BI "int sigtimedwait(const sigset_t *" set ", siginfo_t *" info ", "
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.BI " const struct timespec *" timeout ");"
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.fi
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.sp
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.in -4n
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.in
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.sp
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.BR sigwaitinfo (),
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.BR sigtimedwait ():
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_POSIX_C_SOURCE\ >=\ 199309L
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.SH DESCRIPTION
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.BR sigwaitinfo ()
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suspends execution of the calling process until one of the signals in
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.I set
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is delivered.
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(If one of the signals in
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.I set
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is already pending for the calling process,
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.BR sigwaitinfo ()
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will return immediately with information about that signal.)
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.BR sigwaitinfo ()
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removes the delivered signal from the calling process's list of pending
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signals and returns the signal number as its function result.
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If the
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.I info
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argument is not NULL,
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then it returns a structure of type
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.I siginfo_t
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(see
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.BR sigaction (2))
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containing information about the signal.
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.PP
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Signals returned via
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.BR sigwaitinfo ()
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are delivered in the usual order; see
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.BR signal (7)
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for further details.
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.PP
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.BR sigtimedwait ()
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operates in exactly the same way as
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.BR sigwaitinfo ()
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except that it has an additional argument,
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.IR timeout ,
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which enables an upper bound to be placed on the time for which
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the process is suspended.
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This argument is of the following type:
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.sp
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.in +2n
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.nf
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struct timespec {
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long tv_sec; /* seconds */
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long tv_nsec; /* nanoseconds */
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}
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.fi
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.in -2n
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.sp
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If both fields of this structure are specified as 0, a poll is performed:
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.BR sigtimedwait ()
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returns immediately, either with information about a signal that
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was pending for the caller, or with an error
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if none of the signals in
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.I set
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was pending.
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.SH "RETURN VALUE"
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On success, both
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.BR sigwaitinfo ()
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and
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.BR sigtimedwait ()
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return a signal number (i.e., a value greater than zero).
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On failure both calls return \-1, with
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.I errno
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set to indicate the error.
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.SH ERRORS
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.TP
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.B EAGAIN
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No signal in
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.I set
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was delivered within the
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.I timeout
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period specified to
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.BR sigtimedwait ().
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.TP
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.B EINTR
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The wait was interrupted by a signal handler.
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(This handler was for a signal other than one of those in
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.IR set .)
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.TP
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.B EINVAL
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.I timeout
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was invalid.
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.SH "CONFORMING TO"
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POSIX.1-2001
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.SH NOTES
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In normal usage, the calling program blocks the signals in
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.I set
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via a prior call to
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.BR sigprocmask (2)
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(so that the default disposition for these signals does not occur if they
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are delivered between successive calls to
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.BR sigwaitinfo ()
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or
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.BR sigtimedwait ())
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and does not establish handlers for these signals.
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In a multithreaded program,
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the signal should be blocked in all threads to prevent
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the signal being delivered to a thread other than the one calling
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.BR sigwaitinfo ()
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or
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.BR sigtimedwait ()).
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.PP
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POSIX leaves the meaning of a NULL value for the
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.I timeout
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argument of
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.BR sigtimedwait ()
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unspecified, permitting the possibility that this has the same meaning
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as a call to
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.BR sigwaitinfo (),
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and indeed this is what is done on Linux.
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On Linux,
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.BR sigwaitinfo ()
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is a library function implemented on top of
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.BR sigtimedwait ().
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.SH "SEE ALSO"
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.BR kill (2),
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.BR sigaction (2),
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.BR signal (2),
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.BR sigpending (2),
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.BR sigprocmask (2),
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.BR sigqueue (2),
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.BR sigsetops (3),
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.BR signal (7)
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