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"
  32 .br
  33 .BI "ualarm(unsigned int " usecs ", unsigned int " interval );
  34 .sp
  35 /* SUSv2 version */
  36 .B "#define _XOPEN_SOURCE 500"
  37 .br
  38 .B "#include <unistd.h>"
  39 .sp
  40 .BI "useconds_t ualarm(useconds_t " usecs ", useconds_t " interval );
  41 .fi
  42 .SH DESCRIPTION
  43 The \fBualarm\fP() function causes the signal SIGALRM to be sent
  44 to the invoking process after (not less than)
  45 .I usecs
  46 microseconds.
  47 The delay may be lengthened slightly by any system activity
  48 or by the time spent processing the call or by the
  49 granularity of system timers.
  50 .LP
  51 Unless caught or ignored, this signal will terminate the process.
  52 .LP
  53 If the
  54 .I interval
  55 argument is non-zero, further SIGALRM signals will be sent every
  56 .I interval
  57 microseconds after the first.
  58 .SH "RETURN VALUE"
  59 This function returns the number of microseconds remaining from
  60 the previous call, or 0 when no alarm is pending.
  61 .SH ERRORS
  62 .TP
  63 EINTR
  64 Interrupted by a signal.
  65 .TP
  66 EINVAL
  67 \fIusecs\fP or \fIinterval\fP is not smaller than 1000000.
  68 (On systems where that is considered an error.)
  69 .SH "CONFORMING TO"
  70 4.3BSD, POSIX 1003.1-2003.
  71 4.3BSD, SUSv2 and POSIX do not define any errors.
  72 .SH NOTES
  73 The type
  74 .B useconds_t
  75 is an unsigned integer type capable of holding integers
  76 in the range [0,1000000].
  77 This type is defined by
  78 .I <sys/types.h>
  79 included by
  80 .I <unistd.h>
  81 but glibc defines it only when _XOPEN_SOURCE has a value not less than 500,
  82 or both _XOPEN_SOURCE and _XOPEN_SOURCE_EXTENDED are defined.
  83 .\" useconds_t also gives problems on HPUX 10.
  84 Programs will be more portable if they never mention this type explicitly.
  85 .LP
  86 The interaction of this function with
  87 other timer functions such as
  88 .BR alarm (),
  89 .BR sleep (),
  90 .BR nanosleep (),
  91 .BR setitimer (),
  92 .BR timer_create (),
  93 .BR timer_delete (),
  94 .BR timer_getoverrun (),
  95 .BR timer_gettime (),
  96 .BR timer_settime (),
  97 .BR usleep ()
  98 is unspecified.
  99 .LP
 100 This function is obsolete. Use
 101 .BR nanosleep (2)
 102 or
 103 .BR setitimer (2)
 104 instead.
 105 .SH "SEE ALSO"
 106 .BR alarm (2),
 107 .BR getitimer (2),
 108 .BR nanosleep (2),
 109 .BR select (2),
 110 .BR setitimer (2),
 111 .BR usleep (3)