1*48352Scael.\" Copyright (c) 1986, 1991 Regents of the University of California. 2*48352Scael.\" All rights reserved. 325789Smckusick.\" 4*48352Scael.\" %sccs.include.redist.man% 525789Smckusick.\" 6*48352Scael.\" @(#)usleep.3 6.4 (Berkeley) 04/19/91 7*48352Scael.\" 8*48352Scael.Dd 9*48352Scael.Dt USLEEP 3 10*48352Scael.Os BSD 4.3 11*48352Scael.Sh NAME 12*48352Scael.Nm usleep 13*48352Scael.Nd suspend execution for interval of microseconds 14*48352Scael.Sh SYNOPSIS 15*48352Scael.Fd #include <unistd.h> 16*48352Scael.Ft void 17*48352Scael.Fn usleep "u_int microseconds" 18*48352Scael.Sh DESCRIPTION 19*48352ScaelThe 20*48352Scael.Fn sleep 21*48352Scaelfunction 22*48352Scaelsuspends execution of the calling process 23*48352Scaelfor 24*48352Scael.Fa microseconds 25*48352Scaelof time. 26*48352ScaelSystem activity or time spent in processing the 27*48352Scaelcall may lengthen the sleep slightly. 28*48352Scael.Pp 29*48352ScaelIf a timer is already running on the process its state is saved. 30*48352ScaelIf the value 31*48352Scael.Fa microseconds 32*48352Scaelis more than or equal to the remaining clock time for the saved timer, 33*48352Scaelthe sleep time is set to 34*48352Scaelthe remaining clock time. 35*48352ScaelThe state of the previous timer 36*48352Scaelis restored after 37*48352Scael.Fa microseconds 38*48352Scaelhas passed. 39*48352Scael.Pp 4028215SkarelsThis routine is implemented using 41*48352Scael.Xr setitimer 2 ; 4228215Skarelsit requires eight system calls each time it is invoked. 4328215SkarelsA similar but less compatible function can be obtained with a single 44*48352Scael.Xr select 2 ; 45*48352Scaelsuch a function would not restart after signals, but would not interfere 4628215Skarelswith other uses of 47*48352Scael.Xr setitimer . 48*48352Scael.Sh SEE ALSO 49*48352Scael.Xr setitimer 2 , 50*48352Scael.Xr getitimer 2 , 51*48352Scael.Xr sigpause 2 , 52*48352Scael.Xr ualarm 3 , 53*48352Scael.Xr sleep 3 , 54*48352Scael.Xr alarm 3 55*48352Scael.Sh HISTORY 56*48352ScaelThe 57*48352Scael.Fn usleep 58*48352Scaelfunction appeared in 59*48352Scael.Bx 4.3 . 60