man3/ualarm.3

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  24 .TH UALARM 3  2010-09-20 "" "Linux Programmer's Manual"
  25 .SH NAME
  26 ualarm \- schedule signal after given number of microseconds
  27 .SH SYNOPSIS
  28 .nf
  29 .B "#include <unistd.h>"
  30 .sp
  31 .BI "useconds_t ualarm(useconds_t " usecs ", useconds_t " interval );
  32 .fi
  33 .sp
  34 .in -4n
  35 Feature Test Macro Requirements for glibc (see
  36 .BR feature_test_macros (7)):
  37 .in
  38 .sp
  39 .BR ualarm ():
  40 .ad l
  41 .RS 4
  42 .PD 0
  43 .TP 4
  44 Since glibc 2.12:
  45 .nf
  46 _BSD_SOURCE ||
  47     (_XOPEN_SOURCE\ >=\ 500 ||
  48         _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED) &&
  49     !(_POSIX_C_SOURCE\ >=\ 200809L || _XOPEN_SOURCE\ >=\ 700)
  50 .TP 4
  51 .fi
  52 Before glibc 2.12:
  53 _BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500 ||
  54 _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
  55 .PD
  56 .RE
  57 .ad b
  58 .SH DESCRIPTION
  59 The
  60 .BR ualarm ()
  61 function causes the signal
  62 .B SIGALRM
  63 to be sent to the invoking process after (not less than)
  64 .I usecs
  65 microseconds.
  66 The delay may be lengthened slightly by any system activity
  67 or by the time spent processing the call or by the
  68 granularity of system timers.
  69 .LP
  70 Unless caught or ignored, the
  71 .B SIGALRM
  72 signal will terminate the process.
  73 .LP
  74 If the
  75 .I interval
  76 argument is nonzero, further
  77 .B SIGALRM
  78 signals will be sent every
  79 .I interval
  80 microseconds after the first.
  81 .SH RETURN VALUE
  82 This function returns the number of microseconds remaining for
  83 any alarm that was previously set, or 0 if no alarm was pending.
  84 .SH ERRORS
  85 .TP
  86 .B EINTR
  87 Interrupted by a signal.
  88 .TP
  89 .B EINVAL
  90 \fIusecs\fP or \fIinterval\fP is not smaller than 1000000.
  91 (On systems where that is considered an error.)
  92 .SH CONFORMING TO
  93 4.3BSD, POSIX.1-2001.
  94 POSIX.1-2001 marks
  95 .BR ualarm ()
  96 as obsolete.
  97 POSIX.1-2008 removes the specification of
  98 .BR ualarm ().
  99 4.3BSD, SUSv2, and POSIX do not define any errors.
 100 .SH NOTES
 101 The type
 102 .I useconds_t
 103 is an unsigned integer type capable of holding integers
 104 in the range [0,1000000].
 105 On the original BSD implementation, and in glibc before version 2.1,
 106 the arguments to
 107 .BR ualarm ()
 108 were instead typed as
 109 .IR "unsigned int" .
 110 Programs will be more portable if they never mention
 111 .I useconds_t
 112 explicitly.
 113 .LP
 114 The interaction of this function with
 115 other timer functions such as
 116 .BR alarm (2),
 117 .BR sleep (3),
 118 .BR nanosleep (2),
 119 .BR setitimer (2),
 120 .BR timer_create (2),
 121 .BR timer_delete (2),
 122 .BR timer_getoverrun (2),
 123 .BR timer_gettime (2),
 124 .BR timer_settime (2),
 125 .BR usleep (3)
 126 is unspecified.
 127 .LP
 128 This function is obsolete.
 129 Use
 130 .BR setitimer (2)
 131 or POSIX interval timers
 132 .RB ( timer_create (2),
 133 etc.)
 134 instead.
 135 .SH SEE ALSO
 136 .BR alarm (2),
 137 .BR getitimer (2),
 138 .BR nanosleep (2),
 139 .BR select (2),
 140 .BR setitimer (2),
 141 .BR usleep (3),
 142 .BR time (7)