Synopsis
#include <unistd.h>
unsigned sleep(unsigned seconds);
Status
Partially implemented
Conformance
IEEE Std 1003.1-2017
Description
The sleep() function shall cause the calling thread to be suspended from execution until either the number of realtime
seconds specified by the argument seconds has elapsed or a signal is delivered to the calling thread and its action is to
invoke a signal-catching function or to terminate the process. The suspension time may be longer than requested due to the
scheduling of other activity by the system.
In single-threaded programs, sleep() may make use of SIGALRM. In multi-threaded programs, sleep() shall not make
use of SIGALRM and the remainder of this does not apply.
If a SIGALRM signal is generated for the calling process during execution of sleep() and if the SIGALRM signal is being
ignored or blocked from delivery, it is unspecified whether sleep() returns when the SIGALRM signal is scheduled. If the
signal is being blocked, it is also unspecified whether it remains pending after sleep() returns or it is discarded.
If a SIGALRM signal is generated for the calling process during execution of sleep(), except as a result of a prior call
to alarm(), and if the SIGALRM signal is not being ignored or blocked from delivery,
it is unspecified whether that signal has any effect other than causing sleep() to return.
If a signal-catching function interrupts sleep() and examines or changes either the time a SIGALRM is scheduled to be
generated, the action associated with the SIGALRM signal, or whether the SIGALRM signal is blocked from delivery, the results are
unspecified.
If a signal-catching function interrupts sleep() and calls siglongjmp()
or longjmp() to restore an environment saved prior to the sleep() call, the
action associated with the SIGALRM signal and the time at which a SIGALRM signal is scheduled to be generated are unspecified. It
is also unspecified whether the SIGALRM signal is blocked, unless the signal mask of the process is restored as part of the
environment.
Interactions between sleep() and setitimer() are unspecified.
Return value
If sleep() returns because the requested time has elapsed, the value returned shall be 0. If sleep() returns due
to delivery of a signal, the return value shall be the "unslept" amount (the requested time minus the time actually slept) in
seconds.
Errors
No errors are defined.
Tests
Untested
Known bugs
None