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.Dd September 12, 2019
.Dt SLEEP 1
.Os
.Sh NAME
.Nm sleep
.Nd suspend execution for an interval
.Sh SYNOPSIS
.Nm sleep
.Ar time[suffix]
.Sh DESCRIPTION
.Nm
suspends execution for at least the time in seconds specified by
.Ar time
or until a
.Dv SIGALRM
signal is received.
The
.Ar time
operand can be specified as a non-negative floating point number but the
actual granularity depends on the underlying system.
The
.Ar time
operand may be passed as a decimal or hexadecimal string.
Other floating point values such as Inf or infinity are also honored.
.Pp
A single suffix may be applied to the
.Ar time
operand to represent units other than seconds.
Supported suffixes for the
.Ar suffix
operand include:
.Bl -tag -offset indent -width 6n
.It Sy s
Represents time in seconds.
.It Sy m
Represents time in minutes.
.It Sy h
Represents time in hours.
.It Sy d
Represents time in days.
.It Sy w
Represents time in weeks.
.It Sy y
Represents time in years.
.El
.Pp
The use of suffixes is generally not portable to other systems.
.Ss Signals
If the
.Nm
program receives a signal, unless it is the
.Dv SIGALRM
signal, it will follow with the default signal handling disposition.
If such a signal would interrupt the sleep, then the program may
terminate with an error.
.Sh EXIT STATUS
The following exit values are returned:
.Bl -inset
.It Sy 0
The execution was successfully suspended for at least
.Ar time
seconds, or a
.Dv SIGALRM
signal was received.
.It Sy >0
An error has occurred.
.El
.Sh EXAMPLES
.Sy Example 1
Suspending Command Execution
.Pp
The following example executes a command after a certain amount of time:
.Bd -literal -offset indent
example% \fB(sleep 105; \fIcommand\fR)&\fR
.Ed
.Pp
.Sy Example 2
Executing a Command Every So Often
.Pp
The following example executes a command every so often:
.Bd -literal -offset indent
example% \fBwhile true; do
        \fIcommand\fR
        sleep 37
done\fR
.Ed
.Pp
.Sy Example 3
Suspend command execution forever
.Po
or until a
.Dv SIGALRM
signal is received
.Pc
.Bd -literal
example% sleep Inf
.Ed
.Pp
.Sy Example 4
Suspending command execution for 0.5 seconds
.Pp
Suspending command execution for 0.5 seconds using an alternative
floating-point representation for the value "0.5".
.Bd -literal
example% printf "%a\en" 0.5
0x1.0000000000000000000000000000p-01
example% sleep 0x1.0000000000000000000000000000p-01
.Ed
.Sh ENVIRONMENT VARIABLES
See
.Xr environ 7
for descriptions of the following environment variables
that affect the execution of
.Nm :
.Ev LANG ,
.Ev LC_ALL ,
.Ev LC_MESSAGES ,
.Ev LC_NUMERIC ,
and
.Ev NLSPATH .
.Sh INTERFACE STABILITY
.Sy Committed
.Sh SEE ALSO
.Xr wait 1 ,
.Xr alarm 2 ,
.Xr nanosleep 3C ,
.Xr sleep 3C ,
.Xr environ 7