SLEEPENH(1) General Commands Manual SLEEPENH(1)
NAME
sleepenh - an enhanced sleep program.
SYNOPSIS
sleepenh [initial-time] sleep-time
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 initial-time to a successive exe-
cution 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 exe-
cution 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
BUGS
It is not accurate for a single sleep. Short sleep-times will also not be accurate.
SEE ALSO
date(1), sleep(1).
AUTHOR
This manual page was written by Pedro Zorzenon Neto.
2008/04/20 SLEEPENH(1)