debian man page for sleepenh

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)