freebsd-src/bin/sleep/sleep.1
Konstantin Belousov 67a54762a1 Document the new argument parser for sleep(1) and SIGINFO behaviour.
Remove higlight for the unportability notice.

MFC after:	3 weeks
2010-08-02 10:59:23 +00:00

126 lines
3.7 KiB
Groff

.\"-
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.\" @(#)sleep.1 8.3 (Berkeley) 4/18/94
.\" $FreeBSD$
.\"
.Dd April 18, 1994
.Dt SLEEP 1
.Os
.Sh NAME
.Nm sleep
.Nd suspend execution for an interval of time
.Sh SYNOPSIS
.Nm
.Ar seconds
.Sh DESCRIPTION
The
.Nm
command
suspends execution for a minimum of
.Ar seconds .
.Pp
If the
.Nm
command receives a signal, it takes the standard action.
When the
.Dv SIGINFO
signal is received, the estimate of the amount of seconds left to
sleep is printed on the standard output.
.Sh IMPLEMENTATION NOTES
The
.Dv SIGALRM
signal is not handled specially by this implementation.
.Pp
The
.Nm
command allows and honors a non-integer number of seconds to sleep
in any form acceptable by
.Xr strtod 3 .
This is a non-portable extension, and its use will nearly guarantee that
a shell script will not execute properly on another system.
.Sh EXIT STATUS
.Ex -std
.Sh EXAMPLES
To schedule the execution of a command for
.Va x
number seconds later (with
.Xr csh 1 ) :
.Pp
.Dl (sleep 1800; sh command_file >& errors)&
.Pp
This incantation would wait a half hour before
running the script command_file.
(See the
.Xr at 1
utility.)
.Pp
To reiteratively run a command (with the
.Xr csh 1 ) :
.Pp
.Bd -literal -offset indent -compact
while (1)
if (! -r zzz.rawdata) then
sleep 300
else
foreach i (`ls *.rawdata`)
sleep 70
awk -f collapse_data $i >> results
end
break
endif
end
.Ed
.Pp
The scenario for a script such as this might be: a program currently
running is taking longer than expected to process a series of
files, and it would be nice to have
another program start processing the files created by the first
program as soon as it is finished (when zzz.rawdata is created).
The script checks every five minutes for the file zzz.rawdata,
when the file is found, then another portion processing
is done courteously by sleeping for 70 seconds in between each
awk job.
.Sh SEE ALSO
.Xr nanosleep 2 ,
.Xr sleep 3
.Sh STANDARDS
The
.Nm
command is expected to be
.St -p1003.2
compatible.
.Sh HISTORY
A
.Nm
command appeared in
.At v4 .