HP-UX Reference (11i v1 00/12) - 2 System Calls (vol 5)

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usleep(2) usleep(2)

NAME

usleep - suspend execution for an interval

SYNOPSIS

#include <unistd.h>

int usleep(useconds_t useconds);

DESCRIPTION

The usleep() function will cause the calling thread to be suspended from execution until either the

number of real-time microseconds speciﬁed by the argument useconds 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 activities by the system,

or because of the time spent in processing the call.

The useconds argument must be less than 1,000,000. If the value of useconds is 0, then the call has no

effect.

If a SIGALRM signal is generated for the calling process during execution of

usleep() and if the

SIGALRM signal is being ignored or blocked from delivery, it is unspeciﬁed whether

usleep() returns

when the

SIGALRM signal is scheduled; if the signal is being blocked, it is also unspeciﬁed whether it

remains pending after usleep() returns or it is discarded.

If a SIGALRM signal is generated for the calling process during execution of usleep(), 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 signalhas any effect other than causing usleep() to return.

If a signal-catching function interrupts

usleep() 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 sig-

nal is blocked from delivery, the results are unspeciﬁed.

If a signal-catching function interrupts

usleep() and calls siglongjmp() or longjmp() to restore

an environment saved prior to the usleep() 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 process’s signal mask is restored as part of the environ-

ment.

Implementations may place limitations on the granularity of timer values. For each interval timer, if the

requested timer value requires a ﬁner granularity than the implementation supports, the actual timer

value will be rounded up to the next supported value.

Interactions between usleep() and any of the following are unspeciﬁed: nanosleep() , setiti-

mer()

, timer_create(),

timer_delete(), timer_getoverrun(), timer_gettime()

timer_settime(), ualarm(),

sleep().

RETURN VALUE

On successful completion,

usleep() returns 0. Otherwise, it returns −1 and sets errno to indicate the

error.

ERRORS

The usleep() function may fail if:

[EINVAL] The time interval speciﬁed 1,000,000 or more microseconds.

APPLICATION USAGE

The usleep() function is included for its historical usage. The setitimer() function is preferred over

this function. Multi-threaded applications are recommended to use nanosleep() instead of usleep().

usleep() is also a thread canceling point.