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 .B "#define _XOPEN_SOURCE 500     /* Or: #define _BSD_SOURCE */"
  29 .B "#include <unistd.h>"
  30 .sp
  31 .BI "useconds_t ualarm(useconds_t " usecs ", useconds_t " interval );
  32 .fi
  33 .SH DESCRIPTION
  34 The \fBualarm\fP() function causes the signal SIGALRM to be sent
  35 to the invoking process after (not less than)
  36 .I usecs
  37 microseconds.
  38 The delay may be lengthened slightly by any system activity
  39 or by the time spent processing the call or by the
  40 granularity of system timers.
  41 .LP
  42 Unless caught or ignored, the SIGALRM signal will terminate the process.
  43 .LP
  44 If the
  45 .I interval
  46 argument is non-zero, further SIGALRM signals will be sent every
  47 .I interval
  48 microseconds after the first.
  49 .SH "RETURN VALUE"
  50 This function returns the number of microseconds remaining for
  51 any alarm that was previously set, or 0 if no alarm was pending.
  52 .SH ERRORS
  53 .TP
  54 EINTR
  55 Interrupted by a signal.
  56 .TP
  57 EINVAL
  58 \fIusecs\fP or \fIinterval\fP is not smaller than 1000000.
  59 (On systems where that is considered an error.)
  60 .SH "CONFORMING TO"
  61 4.3BSD, POSIX.1-2001.
  62 POSIX.1-2001 marks
  63 .BR ualarm ()
  64 as obsolete.
  65 4.3BSD, SUSv2, and POSIX do not define any errors.
  66 .SH NOTES
  67 The type
  68 .I useconds_t
  69 is an unsigned integer type capable of holding integers
  70 in the range [0,1000000].
  71 On the original BSD implementation, and in glibc before version 2.1,
  72 the arguments to
  73 .BR ualarm ()
  74 were instead typed as
  75 .IR "unsigned int" .
  76 Programs will be more portable if they never mention
  77 .I useconds_t
  78 explicitly.
  79 .LP
  80 The interaction of this function with
  81 other timer functions such as
  82 .BR alarm (),
  83 .BR sleep (),
  84 .BR nanosleep (),
  85 .BR setitimer (),
  86 .BR timer_create (),
  87 .BR timer_delete (),
  88 .BR timer_getoverrun (),
  89 .BR timer_gettime (),
  90 .BR timer_settime (),
  91 .BR usleep ()
  92 is unspecified.
  93 .LP
  94 This function is obsolete. Use
  95 .BR setitimer (2)
  96 or POSIX interval timers
  97 .RB ( timer_create (),
  98 etc.)
  99 instead.
 100 .SH "SEE ALSO"
 101 .BR alarm (2),
 102 .BR getitimer (2),
 103 .BR nanosleep (2),
 104 .BR select (2),
 105 .BR setitimer (2),
 106 .BR usleep (3),
 107 .BR feature_test_macros (7),
 108 .BR time (7)