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Command: sleep | Section: 1 | Source: NetBSD | File: sleep.1
SLEEP(1) FreeBSD General Commands Manual SLEEP(1)
NAME
sleep - suspend execution for an interval of time
SYNOPSIS
sleep seconds
DESCRIPTION
The sleep utility suspends execution for a minimum of seconds seconds,
then exits. It is usually used to schedule the execution of other
commands (see EXAMPLES below).
Note: The NetBSD sleep command will accept and honor a non-integer number
of specified seconds. Note however, that if the request is for much more
than 2.5 hours, any fractional seconds will be ignored. Permitting non-
integral delays is a non-portable extension, and its use will decrease
the probability that a shell script will execute properly on another
system.
When the SIGINFO signal is received, an estimate of the number of seconds
remaining to sleep is printed on the standard output.
EXIT STATUS
The sleep utility exits with one of the following values:
0 On successful completion, or if the signal SIGALRM was received.
>0 An error occurred.
EXAMPLES
To schedule the execution of a command for 1800 seconds later:
(sleep 1800; sh command_file >errors 2>&1)&
This incantation would wait half an hour before running the script
"command_file". (See the at(1) utility.)
To repeatedly run a command (using csh(1)):
while (1)
if (! -r zzz.rawdata) then
sleep 300
else
foreach i (*.rawdata)
sleep 70
awk -f collapse_data $i >> results
end
break
endif
end
The scenario for a script such as this might be: a program currently
running is taking longer than expected to process a series of files, and
it would be nice to have another program start processing the files
created by the first program as soon as it is finished (when zzz.rawdata
is created). The script checks every five minutes for the file
zzz.rawdata. When the file is found, processing the generated files
(*.rawdata) is done courteously by sleeping for 70 seconds in between
each awk job.
To wait until a particular time, the following, with some error checking
added, might be used (using sh(1) on NetBSD):
END=$(( $( date -d "$1" +%s ) - START_TIME ))
while [ "${SECONDS}" -lt "${END}" ]
do
sleep "$((END - SECONDS))"
done
where the argument `$1' specifies the desired date and time in any format
the -d option to the date(1) command accepts.
SEE ALSO
at(1), csh(1), date(1), sh(1), nanosleep(2), sleep(3)
STANDARDS
The sleep command is expected to be IEEE Std 1003.2 ("POSIX.2")
compatible.
HISTORY
A sleep utility appeared in Version 4 AT&T UNIX. Processing fractional
seconds, and processing the seconds argument respecting the current
locale, was added in NetBSD 1.3. The ability to sleep for extended
periods appeared in NetBSD 9.
BUGS
This sleep command cannot handle requests for durations much longer than
about 250 billion years. Any such attempt will result in an error, and
immediate termination. It is suggested that when there is a need for
sleeps exceeding this period, the sleep command be executed in a loop,
with each individual sleep invocation limited to 200 billion years
approximately.
FreeBSD 14.1-RELEASE-p8 January 26, 2019 FreeBSD 14.1-RELEASE-p8