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SLEEPENH

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 execution 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 execution 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.

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