sleepenh (1) Linux Manual Page
sleepenh – an enhanced sleep program.
Synopsis
sleepenh [initial-time] sleep-timeDescription
sleepenh is a program that can be used when there is a need to execute some functions periodically in a shell script. It was not designed to be accurate for a single sleep, but to be accurate in a sequence of consecutive sleeps.After a successful execution, it returns to stdout the timestamp it finished running, that can be used as initial-time to a successive execution of sleepenh.
Options
There are no command line options. Run it without any option to get a brief help and version.Arguments
sleep-time is a real number in seconds, with microseconds resolution (1 minute, 20 seconds and 123456 microseconds would be 80.123456).initial-time is a real number in seconds, with microseconds resolution. This number is system dependent. In GNU/Linux systems, it is the number of seconds since midnight 1970-01-01 GMT. Do not try to get a good value of initial-time. Use the value supplied by a previous execution of sleepenh.
If you don’t specify initial-time, it is assumed the current-time.
Exit Status
An exit status greater or equal to 10 means failure. Known exit status:- 0
- Success.
- 1
- Success. There was no need to sleep. (means that initial-time + sleep-time was greater than current-time).
- 10
- Failure. Missing command line arguments.
- 11
- Failure. Did not receive SIGALRM.
- 12
- Failure. Argument is not a number.
- 13
- Failure. System error, could not get current time.
Usage Example
Suppose you need to send the char ‘A’ to the serial port ttyS0 every 4 seconds. This will do that:-
#!/bin/sh
TIMESTAMP=`sleepenh 0`
while true; do
#send the byte to ttyS0
echo -n"A" > /dev/ttyS0;
#just print a nice message on screen
echo -n"I sent ‘A’ to ttyS0, time now is ";
sleepenh 0;#
wait the required time
TIMESTAMP=`sleepenh$TIMESTAMP 4.0`;
done
Hint
This program can be used to get the current time. Just execute:- sleepenh 0