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  14 .TH SLEEP 1 "Nov 20, 2007"
  15 .SH NAME
  16 sleep \- suspend execution for an interval
  17 .SH SYNOPSIS
  18 .SS "/usr/bin/sleep"
  19 .LP
  20 .nf
  21 \fB/usr/bin/sleep\fR \fIseconds\fR
  22 .fi
  23 
  24 .SS "ksh93"
  25 .LP
  26 .nf
  27 \fBsleep\fR \fIseconds\fR
  28 .fi
  29 
  30 .SH DESCRIPTION
  31 .sp
  32 .LP
  33 \fBsleep\fR suspends execution for at least the time in seconds specified by
  34 \fIseconds\fR or until a \fBSIGALRM\fR signal is received. The \fIseconds\fR
  35 operand can be specified as a floating point number but the actual granularity
  36 normally depends on the underlying system.
  37 .SH OPERANDS
  38 .SS "/usr/bin/sleep"
  39 .sp
  40 .LP
  41 The following operands are supported for \fB/usr/bin/sleep\fR and \fBksh93\fR's
  42 \fBsleep\fR built-in command:
  43 .sp
  44 .ne 2
  45 .na
  46 \fB\fIseconds\fR\fR
  47 .ad
  48 .RS 11n
  49 A non-negative floating-point number specifying the number of seconds for which
  50 to suspend execution. The floating-point number may be specified in all formats
  51 required by C99/XPG6, including constants such as "Inf" or "infinite".
  52 .RE
  53 
  54 .SS "ksh93"
  55 .sp
  56 .LP
  57 The following operands are supported:
  58 .sp
  59 .ne 2
  60 .na
  61 \fB\fItime\fR\fR
  62 .ad
  63 .RS 8n
  64 Specify \fItime\fR in seconds as a floating point number. The actual
  65 granularity depends on the underlying system, normally around 1 millisecond.
  66 .RE
  67 
  68 .SH EXAMPLES
  69 .LP
  70 \fBExample 1 \fRSuspending Command Execution
  71 .sp
  72 .LP
  73 The following example executes a command after a certain amount of time:
  74 
  75 .sp
  76 .in +2
  77 .nf
  78 example% \fB(sleep 105; \fIcommand\fR)&\fR
  79 .fi
  80 .in -2
  81 .sp
  82 
  83 .LP
  84 \fBExample 2 \fRExecuting a Command Every So Often
  85 .sp
  86 .LP
  87 The following example executes a command every so often:
  88 
  89 .sp
  90 .in +2
  91 .nf
  92 example% \fBwhile true
  93 do
  94         \fIcommand\fR
  95         sleep 37
  96 done\fR
  97 .fi
  98 .in -2
  99 .sp
 100 
 101 .LP
 102 \fBExample 3 \fRSuspend command execution forever (or until a \fBSIGALRM\fR
 103 signal is received)
 104 .sp
 105 .in +2
 106 .nf
 107 example% sleep Inf
 108 .fi
 109 .in -2
 110 .sp
 111 
 112 .LP
 113 \fBExample 4 \fRSuspending command execution for 0.5 seconds
 114 .sp
 115 .LP
 116 Suspending command execution for 0.5 seconds using an alternative
 117 floating-point representation for the value "0.5"
 118 
 119 .sp
 120 .in +2
 121 .nf
 122 example% printf "%a\n" 0.5
 123 0x1.0000000000000000000000000000p-01
 124 .fi
 125 .in -2
 126 .sp
 127 
 128 .sp
 129 .in +2
 130 .nf
 131 example% sleep 0x1.0000000000000000000000000000p-01
 132 .fi
 133 .in -2
 134 .sp
 135 
 136 .SH ENVIRONMENT VARIABLES
 137 .sp
 138 .LP
 139 See \fBenviron\fR(5) for descriptions of the following environment variables
 140 that affect the execution of \fBsleep\fR: \fBLANG\fR, \fBLC_ALL\fR,
 141 \fBLC_CTYPE\fR, \fBLC_MESSAGES\fR, and \fBNLSPATH\fR.
 142 .SH EXIT STATUS
 143 .sp
 144 .LP
 145 The following exit values are returned:
 146 .sp
 147 .ne 2
 148 .na
 149 \fB\fB0\fR\fR
 150 .ad
 151 .RS 6n
 152 The execution was successfully suspended for at least \fItime\fR seconds, or a
 153 \fBSIGALRM\fR signal was received (see NOTES).
 154 .RE
 155 
 156 .sp
 157 .ne 2
 158 .na
 159 \fB\fB>0\fR\fR
 160 .ad
 161 .RS 6n
 162 An error has occurred.
 163 .RE
 164 
 165 .SH ATTRIBUTES
 166 .sp
 167 .LP
 168 See \fBattributes\fR(5) for descriptions of the following attributes:
 169 .SS "/usr/bin/sleep"
 170 .sp
 171 
 172 .sp
 173 .TS
 174 box;
 175 c | c
 176 l | l .
 177 ATTRIBUTE TYPE  ATTRIBUTE VALUE
 178 _
 179 Interface Stability     Committed
 180 _
 181 Standard        See \fBstandards\fR(5).
 182 .TE
 183 
 184 .SS "ksh93"
 185 .sp
 186 
 187 .sp
 188 .TS
 189 box;
 190 c | c
 191 l | l .
 192 ATTRIBUTE TYPE  ATTRIBUTE VALUE
 193 _
 194 Interface Stability     Uncommitted
 195 .TE
 196 
 197 .SH SEE ALSO
 198 .sp
 199 .LP
 200 \fBksh93\fR(1), \fBwait\fR(1), \fBalarm\fR(2), \fBsleep\fR(3C),
 201 \fBwait\fR(3UCB), \fBattributes\fR(5), \fBenviron\fR(5), \fBstandards\fR(5)
 202 .SH NOTES
 203 .sp
 204 .LP
 205 If the \fBsleep\fR utility receives a \fBSIGALRM\fR signal, one of the
 206 following actions is taken:
 207 .RS +4
 208 .TP
 209 .ie t \(bu
 210 .el o
 211 Terminate normally with a zero exit status.
 212 .RE
 213 .RS +4
 214 .TP
 215 .ie t \(bu
 216 .el o
 217 Effectively ignore the signal.
 218 .RE
 219 .sp
 220 .LP
 221 The \fBsleep\fR utility takes the standard action for all other signals.
 222 .sp
 223 .LP
 224 The behavior for input values such as "NaN" (not-a-number) or negative values
 225 is undefined.