0
Success.
sleepenh1
An enhanced sleep program
Usage
sleepenh [[{--warp | -w}]
INITIALTIME]
TIMETOSLEEP
Overview
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 INITIALTIME to a successive execution of sleepenh.
Options
-
-h, --help -
display this help and exit
-
-w, --warp -
warp resulting timestamp, when there is no need to sleep. An immediately following call of sleepenh with the resulting TIMESTAMP would most probably result in a real sleep.
-
-V, --version -
output version information and exit
Arguments
TIMETOSLEEP is a real number in seconds, with microseconds resolution (1 minute, 20 seconds and 123456 microseconds would be 80.123456).
INITIALTIME 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 INITIALTIME. Use the value supplied by a previous execution of sleepenh.
If you don't specify INITIALTIME, it is assumed the current time.
Exit status
An exit status greater or equal to 10 means failure. Known exit status:
-
1 -
Success. There was no need to sleep. (means that INITIALTIME + TIMETOSLEEP 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
History
- Debian 13 (Trixie): the text shown here
- Debian 12 (Bookworm) to Debian 10 (Buster)
- Debian 9 (Stretch)
- Debian 8 (Jessie) to Debian 5.0 (Lenny)
- Debian 4.0 (Etch) to Debian 3.1 (Sarge)
--help since Debian 9 (Stretch);
--version since Debian 9 (Stretch);
--warp since Debian 9 (Stretch);
-V since Debian 9 (Stretch);
-h since Debian 9 (Stretch);
-w since Debian 9 (Stretch).