xref: /freebsd/bin/sleep/sleep.1 (revision 1dfcff294e44d4b45813288ef4095c36abb22f0e)
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32.\"	@(#)sleep.1	8.3 (Berkeley) 4/18/94
33.\" $FreeBSD$
34.\"
35.Dd May 25, 2022
36.Dt SLEEP 1
37.Os
38.Sh NAME
39.Nm sleep
40.Nd suspend execution for an interval of time
41.Sh SYNOPSIS
42.Nm
43.Ar number Ns Op Ar unit
44.Ar ...
45.Sh DESCRIPTION
46The
47.Nm
48command suspends execution for a minimum of
49.Ar number
50seconds (the default, or unit
51.Cm s ) ,
52minutes (unit
53.Cm m ) ,
54hours (unit
55.Cm h ) ,
56or days (unit
57.Cm d ) .
58If multiple arguments are passed, the delay will be the sum of all values.
59.Pp
60If the
61.Nm
62command receives a signal, it takes the standard action.
63When the
64.Dv SIGINFO
65signal is received, the estimate of the amount of seconds left to
66sleep is printed on the standard output.
67.Sh IMPLEMENTATION NOTES
68The
69.Dv SIGALRM
70signal is not handled specially by this implementation.
71.Pp
72The
73.Nm
74command supports other time units than seconds,
75honors a non-integer number of time units to sleep in any form acceptable by
76.Xr strtod 3 ,
77and accepts more than one delay value.
78These are non-portable extensions, but they have also been implemented
79in GNU sh-utils since version 2.0a (released in 2002).
80.Sh EXIT STATUS
81.Ex -std
82.Sh EXAMPLES
83To schedule the execution of a command for
84.Va x
85number seconds later (with
86.Xr csh 1 ) :
87.Pp
88.Dl (sleep 1800; sh command_file >& errors)&
89.Pp
90This incantation would wait a half hour before
91running the script command_file.
92(See the
93.Xr at 1
94utility.)
95.Pp
96To reiteratively run a command (with the
97.Xr csh 1 ) :
98.Pp
99.Bd -literal -offset indent -compact
100while (1)
101	if (! -r zzz.rawdata) then
102		sleep 300
103	else
104		foreach i (`ls *.rawdata`)
105			sleep 70
106			awk -f collapse_data $i >> results
107		end
108		break
109	endif
110end
111.Ed
112.Pp
113The scenario for a script such as this might be: a program currently
114running is taking longer than expected to process a series of
115files, and it would be nice to have
116another program start processing the files created by the first
117program as soon as it is finished (when zzz.rawdata is created).
118The script checks every five minutes for the file zzz.rawdata,
119when the file is found, then another portion processing
120is done courteously by sleeping for 70 seconds in between each
121awk job.
122.Sh SEE ALSO
123.Xr nanosleep 2 ,
124.Xr sleep 3
125.Sh STANDARDS
126The
127.Nm
128command is expected to be
129.St -p1003.2
130compatible.
131.Sh HISTORY
132A
133.Nm
134command appeared in
135.At v4 .
136