Sleep until a given date with subsecond resolution

 sleepenh is an sleep program for using in shell scripts
 that need to perform a loop that repeats at a regular
 time interval, without cumulative errors.
 .
 It supports microsecond resolution.
 .
 You can also specify the time you need between two calls
 of sleepenh.
 .
 Here follows an usage example to clarify its purpose. This
 example sends 'A' to ttyS0 every 1.2 seconds.
   #!/bin/sh
   # does not wait (or wait 0), just to get initial timestamp
   TIMESTAMP=`sleepenh 0`
   while true; do
     # send the byte to ttyS0
     echo -n "A" > /dev/ttyS0;
     # wait until the required time
     TIMESTAMP=`sleepenh $TIMESTAMP 1.200`;
   done
 .
 For more details, please read the manpage.