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SLEEPENH(1) User commands SLEEPENH(1)

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

display this help and exit
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.
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:

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.

2024-12-09 sleepenh