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\" @(#)usleep.3 8.1 (Berkeley) 6/4/93
\"
Dd April 22, 2024
Dt USLEEP 3
Os
Sh NAME
Nm usleep
Nd suspend execution for interval of microseconds
Sh LIBRARY
Lb libc
Sh SYNOPSIS
In unistd.h
Ft int
Fn usleep "useconds_t microseconds"
Sh DESCRIPTION
Bf -symbolic
This interface is obsoleted by
Xr nanosleep 2 .
Ef
Pp
The
Fn usleep
function
suspends execution of the calling process
until either the number of microseconds specified by
Fa microseconds
have elapsed or a signal is delivered to the calling process 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.
Sh RETURN VALUES
On successful completion,
Fn usleep
returns 0.
Otherwise, it returns \-1 and sets
Va errno
to indicate the error.
Sh ERRORS
The
Fn usleep
function may fail if:
Bl -tag -width Er
It Bq Er EINTR
Nm
was interrupted by the delivery of a signal.
El
Sh SEE ALSO
Xr nanosleep 2 ,
Xr sleep 3
Sh STANDARDS
The
Fn usleep
function conforms to
St -xpg4.2 .
It later appeared in the
Tn POSIX
standard, but in
St -p1003.1-2004
it was marked as legacy and the use of
Xr nanosleep 2
was recommended instead.
The
St -p1003.1-2008
revision removed
Fn usleep
from the specification.
Sh HISTORY
The
Fn usleep
function appeared in
Bx 4.3 .
Sh CAVEATS
In
St -p1003.1-2004 ,
Nm
was limited to values of
Fa microseconds
less than one million.
Some implementations, including
Nx
before 10.1, fail immediately with
Er EINVAL
\(em and don't sleep at all \(em if
Fa microseconds
is one million or greater.
