man2/sigwaitinfo.2

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  20 .TH SIGWAITINFO 2 2002-06-07 "Linux 2.4.18" "Linux Programmer's Manual"
  21 .SH NAME
  22 sigwaitinfo, sigtimedwait \- synchronously wait for queued signals
  23 .SH SYNOPSIS
  24 .nf
  25 .B #include <signal.h>
  26 .sp
  27 .BI "int sigwaitinfo(const sigset_t *" set ", siginfo_t *" info ");"
  28 .sp
  29 .BI "int sigtimedwait(const sigset_t *" set ", siginfo_t *" info ", "
  30 .BI "                 const struct timespec *" timeout ");"
  31 .fi
  32 .SH DESCRIPTION
  33 .BR sigwaitinfo ()
  34 suspends execution of the calling process until one of the signals in
  35 .I set
  36 is delivered.
  37 (If one of the signals in
  38 .I set
  39 is already pending for the calling process,
  40 .BR sigwaitinfo ()
  41 will return immediately with information about that signal.)
  42
  43 .BR sigwaitinfo ()
  44 removes the delivered signal from the calling process's list of pending
  45 signals and returns the signal number as its function result.
  46 If the
  47 .I info
  48 argument is not NULL,
  49 then it returns a structure of type
  50 .I siginfo_t
  51 (see
  52 .BR sigaction (2))
  53 containing information about the signal.
  54 .PP
  55 Signals returned via
  56 .BR sigwaitinfo ()
  57 are delivered in the usual order; see
  58 .BR signal (7)
  59 for further details.
  60 .PP
  61 .BR sigtimedwait ()
  62 operates in exactly the same way as
  63 .BR sigwaitinfo ()
  64 except that it has an additional argument,
  65 .IR timeout ,
  66 which enables an upper bound to be placed on the time for which
  67 the process is suspended.
  68 This argument is of the following type:
  69 .sp
  70 .in +2n
  71 .nf
  72 struct timespec {
  73     long    tv_sec;         /* seconds */
  74     long    tv_nsec;        /* nanoseconds */
  75 }
  76 .fi
  77 .in -2n
  78 .sp
  79 If both fields of this structure are specified as 0, a poll is performed:
  80 .BR sigtimedwait ()
  81 returns immediately, either with information about a signal that
  82 was pending for the caller, or with an error
  83 if none of the signals in
  84 .I set
  85 was pending.
  86 .SH "RETURN VALUE"
  87 On success, both
  88 .BR sigwaitinfo ()
  89 and
  90 .BR sigtimedwait ()
  91 return a signal number (i.e., a value greater than zero).
  92 On failure both calls return \-1, with
  93 .I errno
  94 set to indicate the error.
  95 .SH ERRORS
  96 .TP
  97 .B EAGAIN
  98 No signal in
  99 .I set
 100 was delivered within the
 101 .I timeout
 102 period specified to
 103 .BR sigtimedwait ().
 104 .TP
 105 .B EINTR
 106 The wait was interrupted by a signal handler.
 107 (This handler was for a signal other than one of those in
 108 .IR set .)
 109 .TP
 110 .B EINVAL
 111 .I timeout
 112 was invalid.
 113 .SH NOTES
 114 In normal usage, the calling program blocks the signals in
 115 .I set
 116 via a prior call to
 117 .BR sigprocmask ()
 118 (so that the default disposition for these signals does not occur if they
 119 are delivered between successive calls to
 120 .BR sigwaitinfo ()
 121 or
 122 .BR sigtimedwait ())
 123 and does not establish handlers for these signals.
 124 In a multithreaded program,
 125 the signal should be blocked in all threads to prevent
 126 the signal being delivered to a thread other than the one calling
 127 .BR sigwaitinfo ()
 128 or
 129 .BR sigtimedwait ()).
 130 .PP
 131 POSIX leaves the meaning of a NULL value for the
 132 .I timeout
 133 argument of
 134 .BR sigtimedwait ()
 135 unspecified, permitting the possibility that this has the same meaning
 136 as a call to
 137 .BR sigwaitinfo (),
 138 and indeed this is what is done on Linux.
 139 .SH "CONFORMING TO"
 140 POSIX.1-2001
 141 .SH "SEE ALSO"
 142 .BR kill (2),
 143 .BR sigaction (2),
 144 .BR signal (2),
 145 .BR sigpending (2),
 146 .BR sigprocmask (2),
 147 .BR sigqueue (2),
 148 .BR sigsetops (3),
 149 .BR signal (7)