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.TH SLEEP 1 "May 13, 2017"
.SH NAME
sleep \- suspend execution for an interval
.SH SYNOPSIS
.SS "/usr/bin/sleep"
.LP
.nf
\fB/usr/bin/sleep\fR \fIseconds\fR
.fi

.SS "ksh93"
.LP
.nf
\fBsleep\fR \fIseconds\fR
.fi

.SH DESCRIPTION
.LP
\fBsleep\fR suspends execution for at least the time in seconds specified by
\fIseconds\fR or until a \fBSIGALRM\fR signal is received. The \fIseconds\fR
operand can be specified as a floating point number but the actual granularity
normally depends on the underlying system.
.SH OPERANDS
.SS "/usr/bin/sleep"
.LP
The following operands are supported for \fB/usr/bin/sleep\fR and \fBksh93\fR's
\fBsleep\fR built-in command:
.sp
.ne 2
.na
\fB\fIseconds\fR\fR
.ad
.RS 11n
A non-negative floating-point number specifying the number of seconds for which
to suspend execution. The floating-point number may be specified in all formats
required by C99/XPG6, including constants such as "Inf" or "infinity".
.RE

.SS "ksh93"
.LP
The following operands are supported:
.sp
.ne 2
.na
\fB\fItime\fR\fR
.ad
.RS 8n
Specify \fItime\fR in seconds as a floating point number. The actual
granularity depends on the underlying system, normally around 1 millisecond.
.RE

.SH EXAMPLES
.LP
\fBExample 1 \fRSuspending Command Execution
.sp
.LP
The following example executes a command after a certain amount of time:

.sp
.in +2
.nf
example% \fB(sleep 105; \fIcommand\fR)&\fR
.fi
.in -2
.sp

.LP
\fBExample 2 \fRExecuting a Command Every So Often
.sp
.LP
The following example executes a command every so often:

.sp
.in +2
.nf
example% \fBwhile true
do
        \fIcommand\fR
        sleep 37
done\fR
.fi
.in -2
.sp

.LP
\fBExample 3 \fRSuspend command execution forever (or until a \fBSIGALRM\fR
signal is received)
.sp
.in +2
.nf
example% sleep Inf
.fi
.in -2
.sp

.LP
\fBExample 4 \fRSuspending command execution for 0.5 seconds
.sp
.LP
Suspending command execution for 0.5 seconds using an alternative
floating-point representation for the value "0.5"

.sp
.in +2
.nf
example% printf "%a\en" 0.5
0x1.0000000000000000000000000000p-01
.fi
.in -2
.sp

.sp
.in +2
.nf
example% sleep 0x1.0000000000000000000000000000p-01
.fi
.in -2
.sp

.SH ENVIRONMENT VARIABLES
.LP
See \fBenviron\fR(5) for descriptions of the following environment variables
that affect the execution of \fBsleep\fR: \fBLANG\fR, \fBLC_ALL\fR,
\fBLC_CTYPE\fR, \fBLC_MESSAGES\fR, and \fBNLSPATH\fR.
.SH EXIT STATUS
.LP
The following exit values are returned:
.sp
.ne 2
.na
\fB\fB0\fR\fR
.ad
.RS 6n
The execution was successfully suspended for at least \fItime\fR seconds, or a
\fBSIGALRM\fR signal was received (see NOTES).
.RE

.sp
.ne 2
.na
\fB\fB>0\fR\fR
.ad
.RS 6n
An error has occurred.
.RE

.SH ATTRIBUTES
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.SS "/usr/bin/sleep"
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Committed
_
Standard	See \fBstandards\fR(5).
.TE

.SS "ksh93"
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Uncommitted
.TE

.SH SEE ALSO
.LP
\fBksh93\fR(1), \fBwait\fR(1), \fBalarm\fR(2), \fBsleep\fR(3C),
\fBattributes\fR(5), \fBenviron\fR(5), \fBstandards\fR(5)
.SH NOTES
.LP
If the \fBsleep\fR utility receives a \fBSIGALRM\fR signal, one of the
following actions is taken:
.RS +4
.TP
.ie t \(bu
.el o
Terminate normally with a zero exit status.
.RE
.RS +4
.TP
.ie t \(bu
.el o
Effectively ignore the signal.
.RE
.sp
.LP
The \fBsleep\fR utility takes the standard action for all other signals.
.sp
.LP
The behavior for input values such as "NaN" (not-a-number) or negative values
is undefined.