1 .\" Copyright (c) 2003 Andries Brouwer (aeb@cwi.nl)
3 .\" %%%LICENSE_START(GPLv2+_DOC_FULL)
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24 .TH UALARM 3 2016-03-15 "" "Linux Programmer's Manual"
26 ualarm \- schedule signal after given number of microseconds
29 .B "#include <unistd.h>"
31 .BI "useconds_t ualarm(useconds_t " usecs ", useconds_t " interval );
35 Feature Test Macro Requirements for glibc (see
36 .BR feature_test_macros (7)):
46 (_XOPEN_SOURCE\ >=\ 500) && ! (_POSIX_C_SOURCE\ >=\ 200809L)
47 || /* Glibc since 2.19: */ _DEFAULT_SOURCE
48 || /* Glibc versions <= 2.19: */ _BSD_SOURCE
52 _BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500
53 .\" || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
60 function causes the signal
62 to be sent to the invoking process after (not less than)
65 The delay may be lengthened slightly by any system activity
66 or by the time spent processing the call or by the
67 granularity of system timers.
69 Unless caught or ignored, the
71 signal will terminate the process.
75 argument is nonzero, further
77 signals will be sent every
79 microseconds after the first.
81 This function returns the number of microseconds remaining for
82 any alarm that was previously set, or 0 if no alarm was pending.
86 Interrupted by a signal; see
90 \fIusecs\fP or \fIinterval\fP is not smaller than 1000000.
91 (On systems where that is considered an error.)
93 For an explanation of the terms used in this section, see
99 Interface Attribute Value
102 T} Thread safety MT-Safe
105 4.3BSD, POSIX.1-2001.
109 POSIX.1-2008 removes the specification of
111 4.3BSD, SUSv2, and POSIX do not define any errors.
113 POSIX.1-2001 does not specify what happens if the
116 .\" This case is not documented in HP-US, Solar, FreeBSD, NetBSD, or OpenBSD!
117 On Linux (and probably most other systems),
118 the effect is to cancel any pending alarm.
122 is an unsigned integer type capable of holding integers
123 in the range [0,1000000].
124 On the original BSD implementation, and in glibc before version 2.1,
127 were instead typed as
129 Programs will be more portable if they never mention
133 The interaction of this function with
134 other timer functions such as
139 .BR timer_create (2),
140 .BR timer_delete (2),
141 .BR timer_getoverrun (2),
142 .BR timer_gettime (2),
143 .BR timer_settime (2),
147 This function is obsolete.
150 or POSIX interval timers
151 .RB ( timer_create (2),