USLEEP(3) BSD Programmer's Manual USLEEP(3)
usleep - suspend execution for interval of microseconds
#include <unistd.h> int usleep(useconds_t microseconds);
The usleep() function suspends execution of the calling process for microseconds microseconds of time. System activity or time spent in pro- cessing the call may lengthen the sleep slightly. This routine is implemented using nanosleep(2); it requires one system call each time it is invoked. A similar but less compatible function can be obtained with a single select(2); such a function would not restart after signals, and also does not interfere with other uses of setitimer(2) (not that usleep() interferes with interval timers anymore).
If the usleep() function returns because the requested time has elapsed, the value returned will be zero. If the usleep() function returns due to the delivery of a signal, the value returned will be -1, and the global variable errno will be set to indicate the interruption.
If any of the following conditions occur, the usleep() function shall re- turn -1 and set errno to the corresponding value. [EINTR] usleep() was interrupted by the delivery of a signal. [EINVAL] microseconds specified a value of 1,000,000 or more mi- croseconds.
A microsecond is 0.000001 seconds.
getitimer(2), nanosleep(2), setitimer(2), alarm(3), sigpause(3), sleep(3), ualarm(3)
The usleep() function conforms to X/Open Portability Guide Issue 4.2 ("XPG4.2").
The usleep() function appeared in 4.3BSD. MirOS BSD #10-current November 4, 1997 1
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