sleep(1) - NetBSD Manual Pages

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SLEEP(1)                NetBSD General Commands Manual                SLEEP(1)

sleep -- suspend execution for an interval of time
sleep seconds
The sleep utility suspends execution for a minimum of seconds seconds, then exits. It is usually used to schedule the execution of other com- mands (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 sys- tem. When the SIGINFO signal is received, an estimate of the number of seconds remaining to sleep is printed on the standard output.
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.
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 $i >> results end break endif end The scenario for a script such as this might be: a program currently run- ning is taking longer than expected to process a series of files, and it would be nice to have another program start processing the files created by the first program as soon as it is finished (when zzz.rawdata is created). The script checks every five minutes for the file zzz.rawdata. When the file is found, processing the generated files (*.rawdata) is done courteously by sleeping for 70 seconds in between each awk job. To wait until a particular time, the following, with some error checking added, might be used (using sh(1) on NetBSD): END=$(( $( 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.
at(1), csh(1), date(1), sh(1), nanosleep(2), sleep(3)
The sleep command is expected to be IEEE Std 1003.2 (``POSIX.2'') compat- ible.
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 peri- ods appeared in NetBSD 9.0.
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. NetBSD 10.99 January 26, 2019 NetBSD 10.99
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