man3/ualarm.3

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  23 .TH UALARM 3  2003-07-24 "" "Linux Programmer's Manual"
  24 .SH NAME
  25 ualarm \- schedule signal after given number of microseconds
  26 .SH SYNOPSIS
  27 .nf
  28 /* BSD version */
  29 .B "#include <unistd.h>"
  30 .sp
  31 .BI "unsigned int ualarm(unsigned int " usecs ", unsigned int " interval );
  32 .sp
  33 /* SUSv2 version */
  34 .B "#define _XOPEN_SOURCE 500"
  35 .br
  36 .B "#include <unistd.h>"
  37 .sp
  38 .BI "useconds_t ualarm(useconds_t " usecs ", useconds_t " interval );
  39 .fi
  40 .SH DESCRIPTION
  41 The \fBualarm\fP() function causes the signal SIGALRM to be sent
  42 to the invoking process after (not less than)
  43 .I usecs
  44 microseconds.
  45 The delay may be lengthened slightly by any system activity
  46 or by the time spent processing the call or by the
  47 granularity of system timers.
  48 .LP
  49 Unless caught or ignored, this signal will terminate the process.
  50 .LP
  51 If the
  52 .I interval
  53 argument is non-zero, further SIGALRM signals will be sent every
  54 .I interval
  55 microseconds after the first.
  56 .SH "RETURN VALUE"
  57 This function returns the number of microseconds remaining from
  58 the previous call, or 0 when no alarm is pending.
  59 .SH ERRORS
  60 .TP
  61 EINTR
  62 Interrupted by a signal.
  63 .TP
  64 EINVAL
  65 \fIusecs\fP or \fIinterval\fP is not smaller than 1000000.
  66 (On systems where that is considered an error.)
  67 .SH "CONFORMING TO"
  68 4.3BSD, POSIX.1-2001.
  69 4.3BSD, SUSv2 and POSIX do not define any errors.
  70 .SH NOTES
  71 The type
  72 .B useconds_t
  73 is an unsigned integer type capable of holding integers
  74 in the range [0,1000000].
  75 This type is defined by
  76 .I <sys/types.h>
  77 included by
  78 .I <unistd.h>
  79 but glibc defines it only when _XOPEN_SOURCE has a value not less than 500,
  80 or both _XOPEN_SOURCE and _XOPEN_SOURCE_EXTENDED are defined.
  81 .\" useconds_t also gives problems on HP-UX 10.
  82 Programs will be more portable if they never mention this type explicitly.
  83 .LP
  84 The interaction of this function with
  85 other timer functions such as
  86 .BR alarm (),
  87 .BR sleep (),
  88 .BR nanosleep (),
  89 .BR setitimer (),
  90 .BR timer_create (),
  91 .BR timer_delete (),
  92 .BR timer_getoverrun (),
  93 .BR timer_gettime (),
  94 .BR timer_settime (),
  95 .BR usleep ()
  96 is unspecified.
  97 .LP
  98 This function is obsolete. Use
  99 .BR nanosleep (2)
 100 or
 101 .BR setitimer (2)
 102 instead.
 103 .SH "SEE ALSO"
 104 .BR alarm (2),
 105 .BR getitimer (2),
 106 .BR nanosleep (2),
 107 .BR select (2),
 108 .BR setitimer (2),
 109 .BR usleep (3),
 110 .BR feature_test_macros (7)