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usleep(3) [mojave man page]

USLEEP(3)						   BSD Library Functions Manual 						 USLEEP(3)

NAME
usleep -- suspend thread execution for an interval measured in microseconds LIBRARY
Standard C Library (libc, -lc) SYNOPSIS
#include <unistd.h> int usleep(useconds_t microseconds); DESCRIPTION
The usleep() function suspends execution of the calling thread until either microseconds microseconds have elapsed or a signal is delivered to the thread and its action is to invoke a signal-catching function or to terminate the process. System activity or limitations may lengthen the sleep by an indeterminate amount. This function is implemented using nanosleep(2) by pausing for microseconds microseconds or until a signal occurs. Consequently, in this implementation, sleeping has no effect on the state of process timers, and there is no special handling for SIGALRM. Also, this implementa- tion does not put a limit on the value of microseconds (other than that limited by the size of the useconds_t type); some other platforms require it to be less than one million. NOTE
The usleep() function is obsolescent. Use nanosleep(2) instead. RETURN VALUES
The usleep() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error. ERRORS
The usleep() function will fail if: [EINTR] A signal was delivered to the process and its action was to invoke a signal-catching function. SEE ALSO
nanosleep(2), sleep(3) HISTORY
The usleep() function appeared in 4.3BSD. BSD
February 13, 1998 BSD

Check Out this Related Man Page

SLEEP(3)						   BSD Library Functions Manual 						  SLEEP(3)

NAME
sleep -- suspend thread execution for an interval measured in seconds LIBRARY
Standard C Library (libc, -lc) SYNOPSIS
#include <unistd.h> unsigned int sleep(unsigned int seconds); DESCRIPTION
The sleep() function suspends execution of the calling thread until either seconds seconds have elapsed or a signal is delivered to the thread and its action is to invoke a signal-catching function or to terminate the thread or process. System activity may lengthen the sleep by an indeterminate amount. This function is implemented using nanosleep(2) by pausing for seconds seconds or until a signal occurs. Consequently, in this implementa- tion, sleeping has no effect on the state of process timers, and there is no special handling for SIGALRM. RETURN VALUES
If the sleep() function returns because the requested time has elapsed, the value returned will be zero. If the sleep() function returns due to the delivery of a signal, the value returned will be the unslept amount (the requested time minus the time actually slept) in seconds. SEE ALSO
nanosleep(2), usleep(3) STANDARDS
The sleep() function conforms to ISO/IEC 9945-1:1990 (``POSIX.1''). HISTORY
A sleep() function appeared in Version 7 AT&T UNIX. BSD
February 13, 1998 BSD
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