SLEEPENH

NAME

sleepenh - an enhanced sleep program

SYNOPSIS

sleepenh [[--warp|-w] INITIALTIME] TIMETOSLEEP

DESCRIPTION

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:

	0		Success.
	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

BUGS

It is not accurate for a single sleep. Short TIMETOSLEEPs will also not be accurate.

SEE ALSO

date(1), sleep(1).

AUTHOR

This manual page was written by Pedro Zorzenon Neto.