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#1zz
July 20, 1989 NazCron V1.0 - Cron type event manager Page 1
Overview
--------
NazCron executes CLI commands and programs that can be started
from a CLI at those times you specify in an event list. This
event list is a memory resident list that can be loaded from the
file named CRONTAB located in the S: directory and/or from ARexx
scripts. Every minute, NazCron examines the file timestamp. If
it has changed in the last minute it reloads the event list from
the CRONTAB file. NazCron then searches the event list for all
commands that need to be executed, executes each such command and
then issues a timer request to be re-activated a minute later.
NazCron accepts the Unix Cron file format (see below) with minor
improvements, establishes itself as an ARexx host process and
operates in the background by disconnecting itself from the
initiating CLI. A number of functions are controlled through the
ARexx interface asynchronously to event timing, i.e all such
functions are executed as soon as the initiating ARexx command
message is retrieved from the public message port.
NazCron is a redesign and rewrite of an Amiga public domain
program called AmiCron which, in turn, is an Amiga version of the
Unix program Cron.
Written by
----------
Don Nafis
NazCron may be copied and freely distributed for personal use.
NazCron is shareware, user-supported software. If you like
NazCron and continue to use it after a trial period, please send
the $10 shareware fee to the address listed on the following page
and become a registered user. As a registered user, you will be
assured of timely information on upgrades, you will be given
membership in the support section of our BBS, Viva! Amiga!, and
you will feel good about contributing to the development of new
utility programs for the Amiga. By supporting all shareware
authors, you will be in the driver's seat when it comes to
deciding where future Amiga programs will be going; you will have
a loud voice when we programmers are trying to hear what Amiga
owners want in programs of the future.
Copyright 1989 by Don Nafis and Nazlo Associates Ltd. All rights reserved.
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July 20, 1989 NazCron V1.0 - Cron type event manager Page 2
Send your check for $10.00 to
Don Nafis
Nazlo Associates Ltd.
P.O. Box 1515
Laurel Springs, NJ 08021
Please make your check payable to "Nazlo Associates Ltd.".
Commercial vendors may distribute NazCron with their products as
long as they distribute all files provided here and make it clear
that NazCron is shareware. Before distributing NazCron with your
package, you must send for written permission. This way I can
make sure that you will be distributing the latest version.
If you find this program lacking in any way and thus choose not
to register, I would like to hear your suggestions or complaints.
Please contact me at one of the following and give me a piece of
your mind:
Nazlo Associates Ltd.
P.O. Box 1515
Laurel Springs, NJ 08021
(609) 228-8088 Voice
(609) 227-8278 BBS -
Viva! Amiga!
3/12/24 - 8/N/1 - 24 hours
130 Megabytes Online
Compuserve 70656, 133
Usage
-----
From the CLI, type:
NazCron<cr>
NazCron detaches itself from the initiating CLI as soon as it
begins execution. Thus you can terminate the CLI, endcli, and
let NazCron go on working in the background.
From the Workbench:
Place the pointer on the NazCron Icon and double click with
the left mouse button.
Copyright 1989 by Don Nafis and Nazlo Associates Ltd. All rights reserved.
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July 20, 1989 NazCron V1.0 - Cron type event manager Page 3
You will see no evidence that NazCron has begun executing in
either case unless you have a command in your CRONTAB that sends
a message to the console. Should you panic and start NazCron
again, either from the CLI or Workbench, NazCron will detect that
there is a version already started and retire gracefully with no
harm done.
NazCron begins execution by loading the event list from the file
CRONTAB located in the S: directory. (See below for the CRONTAB
file format.) If CRONTAB is not present, NazCron simply waits
for further instruction through its ARexx port. Since NazCron
doesn't need ARexx to run, it makes no attempt to determine if
ARexx is installed on the system. Therefore you need not start
REXXMAST before you start NazCron. If you have neither a CRONTAB
file in the S: directory nor ARexx, you will simply waste memory
by starting the program because you will be handling no events
and you have no way of terminating NazCron.
Note that in order to detach itself completely from the
initiating CLI, NazCron must open a zero length file named
"ram:*". This is a kludge to get around a quirk in "nil:" file
handling in the Execute() function of AmigaDos (no relation to
the AmigaDOS Execute command in the C: directory). This file
will do no harm and, after terminating NazCron, you may delete
the it with no ill effects.
CRONTAB event format
--------------------
The CRONTAB file is an ASCII text file which you must create with
a text editor and place in the S: directory. Each entry in the
CRONTAB file is either a comment or a event. Each entry must
begin in column 1 with the individual parameters separated by
"white space", i.e. one or more spaces or tabs.
The entry format is:
; comment
- or -
[eventname] min hour day month weekday eventcommand
Where:
[eventname] - an optional name you can supply which
identifies the event for ARexx processing. If you don't
supply a name, the event will be invisible to ARexx scripts.
"eventname" must begin with an alpha character. You can
specify as many events as you wish with the same eventname,
Copyright 1989 by Don Nafis and Nazlo Associates Ltd. All rights reserved.
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July 20, 1989 NazCron V1.0 - Cron type event manager Page 4
but ARexx commands that use "eventname" will only affect the
first event encountered, so it doesn't make any sense to do
so. Since "eventname" is not used for actual event
processing, each identically named event will be processed.
Note, "eventname" is not case sensitive, NazCron converts
all event names to uppercase before adding them to the event
list. Thus "ImportantEvent" and "IMPORTANTEVENT" are the
same eventnames for NazCron purposes.
The remainder of the fields are required.
min - the minute at which "eventcommand" will be executed.
Code the actual minute, minutes, range of minutes or "*" to
indicate every minute. The numeric values may be provided
as:
a single minute, e.g. 5
a group of minutes, e.g. 0,10,20,30
a range of minutes, e.g. 30-45
or a combination, e.g. 0,10,30,47-50,59
hour, day, month and weekday - use the same format as "min".
Ranges of time values are:
min: 0-59
hour: 0-23 (0 = midnight)
day: 1-31 (day is not checked for month. This
means that day 31, month 2 will be
allowed but, of course, never executed)
month: 1-12
weekday: 0-6 (0=Sunday, 6=Saturday)
eventcommand - is the AmigaDOS CLI command to be executed.
It must contain all parameters as if typed from a CLI. Note
that there will be no CLI window for this command's output.
If you wish to see the output, you must use redirection when
you type the command.
Example:
Date >ram:date
Redirection is indicated by the ">" character. Output that
would normally be sent to the CLI window for this command
would, instead, be sent to the file ram:date.
Cron event examples
-------------------
* * * * * Date
Executes the ADOS Date command every minute. Since re-
direction was not specified in the command, you will see no
Copyright 1989 by Don Nafis and Nazlo Associates Ltd. All rights reserved.
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July 20, 1989 NazCron V1.0 - Cron type event manager Page 5
evidence that Date was actually executed.
DateToRam * * * * * Date >ram:date
Also executes the ADOS Date command every minute but the
date is written to the file "date" on the ram: disk. Note,
"DateToRam" is the event name for this event, allowing it to
be manipulated from an ARexx script.
0 19 * * * NewShell "newcon:0/30/640/30/BIX Time" from s:Bixtime
At 7pm every day, a shell will be opened, initially
executing the startup script "Bixtime" from the S:
directory. This script is probably a reminder that it is
now ok to logon to BIX for non-prime time access. The
script "Bixtime" might look something like:
echo "It is 7pm. It is now ok to logon to BIX"
wait 10
endcli
0 10 * * 6 Access!
Every Saturday at 10am, NazCron will initiate the terminal
program Access!
0 0,12,17 * * 1-5 Execute ChangingOfTheGuard
The script "ChangingOfTheGuard" will be executed at
midnight, noon and 5pm every Monday through Friday.
ARexx command processing
------------------------
NazCron supports a rich body of commands that may be introduced
from ARexx scripts or other ARexx interfaced programs. In order
to send these commands to NazCron, the ARexx script must execute
the ARexx "address NAZCRON" statement prior to sending any
NazCron commands. "NAZCRON" (note that this MUST be uppercase)
is the NazCron ARexx host address and must be the current host
when any NazCron command is invoked. Consult the ARexx manual
for further information on communicating with ARexx host
processes.
The return code settings for all commands will be the standard
ARexx values as defined in the ARexx supplied header file
"errors.h". These values are:
RC_OK = 0
RC_WARN = 5
RC_ERROR = 10
RC_FATAL = 20
NazCron returns RC_OK when execution has completed successfully
Copyright 1989 by Don Nafis and Nazlo Associates Ltd. All rights reserved.
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July 20, 1989 NazCron V1.0 - Cron type event manager Page 6
and RC_WARN when a secondary result should have been returned
from the command but the script did not execute the 'options
results' statement. RC_ERROR is returned for most errors
including unrecognized command and errors in command syntax.
RC_FATAL is returned when NazCron is unable to allocate enough
memory to return the secondary result, or if a command is
received after shutdown is under way.
Individual NazCron ARexx commands
---------------------------------
SHUTDOWN
Terminates NazCron immediately. All outstanding events are
purged and the timer is stopped. No events will be executed
after SHUTDOWN is received, even if a timeout was about to
occur.
SUSPEND
All event processing will be stopped until a RESUME is sent.
NazCron will stop looking at events in the event list and
will ignore the CRONTAB file, even if the file has been
modified. All ARexx commands may be executed and events in
the event list may still be manipulated with ARexx commands.
RESUME
Resumes all event processing.
LOCK_EVENTS
This locks file events in the event list. Normally, the
CRONTAB file info block is examined each minute to determine
if the contents of the file have changed. If the file
timestamp is different from the timestamp recorded the last
time the file was loaded, all events loaded from the file
are purged from the event list and the file is reloaded into
the event list. CRONTAB date checking is NOT done when
events are locked. If you are processing a CRONTAB file
that never changes, you can LOCK_EVENTS, thereby eliminating
the unnecessary overhead of examining the CRONTAB file each
minute. Events may still be added or deleted from the event
list via ARexx commands; only the CRONTAB events are locked.
UNLOCK_EVENTS
This unlocks the file events in the event list. After this
command is executed, the CRONTAB file will be examined again
each minute.
NEW_EVENT_FILE filename
"filename" must be the full path/file name of a new CRONTAB
file. NazCron begins processing from the new file
Copyright 1989 by Don Nafis and Nazlo Associates Ltd. All rights reserved.
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July 20, 1989 NazCron V1.0 - Cron type event manager Page 7
immediately. If events are "locked" (see LOCK_EVENTS above)
"filename" will be the file to be used once events have been
unlocked again. Note that it is not necessary to issue
CLOSE_EVENT_FILE prior to opening a new file. Caution:
while NazCron assures that the file exists before doing the
switch, it does not verify the contents of the file.
Consequently, the command may return with a successful
execution masking an error in the contents of the file. If
there is a syntax error in the new file, all file events
will be purged.
CLOSE_EVENT_FILE
Purges all events previously loaded from the event file and
stops examining the file. Only ARexx introduced events will
be processed until the NEW_EVENT_FILE command is executed.
ADD_EVENT cronevent
Adds "cronevent" to the event list. "cronevent" must be in
the same format as defined above. Note that if "eventname"
is not supplied, the event will be invisible to most ARexx
commands.
DELETE_REXX_EVENT eventname
Deletes the event with "eventname" from the event list only
if the event was added from an ARexx script. This command
may not be used to delete a CRONTAB event. If the event
doesn't exist, RC_ERROR is set. If there are more than one
ARexx event in the event list with the same "eventname",
only the first one in the list will be deleted.
DELETE_EVENT eventname
Deletes any event with "eventname" from the event list. If
the event doesn't exist, RC_ERROR is set. If there are more
than one event in the event list with the same "eventname",
only the first one in the list will be deleted.
PURGE_REXX_EVENTS
Deletes all ARexx introduced events from the event list,
even those that are invisible. Events loaded from CRONTAB
will remain in the list untouched.
SHOW_EVENT eventname
Returns the actual ASCII cronevent string in the 'result'
variable for the event named "eventname". If the event
doesn't exist, RC_ERROR is set. Both ARexx and CRONTAB
introduced events may be retrieved. If there are more than
one event in the event list with the same "eventname", only
the first one in the list will be returned.
LIST_EVENTS
Copyright 1989 by Don Nafis and Nazlo Associates Ltd. All rights reserved.
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July 20, 1989 NazCron V1.0 - Cron type event manager Page 8
Returns the eventnames of all named events in the event list
as a string of names separated by blanks. If there are more
than one event in the event list with the same "eventname",
all will be returned. Note, this command makes no
differentiation between events introduced by ARexx commands
and CRONTAB loaded events.
SHOW_STATUS
Returns the status of NazCron. The format of the returned
message is:
eventstate filestate cronfilename
where "eventstate" is either "ACTIVE" or "SUSPENDED",
"filestate" is either "LOCKED" or "UNLOCKED", and
"cronfilename" is the full path name of the current event
file.
NazCron ARexx script example
----------------------------
/* NazCron ARexx script example*/
/* Make sure we send all of our commands to NazCron */
address 'NAZCRON'
/* Don't bother looking at the file again, it will not change */
'LOCK_EVENTS'
'ADD_EVENT sidevent 48 15 * * * dh1:sid'
if (rc ~= 0) then say "ADD_EVENT error "|| rc
'ADD_EVENT myevent * * * * * date >ram:rexxcron.date'
if (rc ~= 0) then say "ADD_EVENT error "|| rc
'ADD_EVENT anotherevent * * * * * date >ram:anotherrexxcron.date'
if (rc ~= 0) then say "ADD_EVENT error "|| rc
/* Get a list of all named events */
options results
'LIST_EVENTS'
if (rc ~= 0) then say "LIST_EVENTS error " || rc
else
do
eventlist = result
/* display the names */
say eventlist
numwords = words(eventlist)
/* If the list isn't empty, display the event connected with
Copyright 1989 by Don Nafis and Nazlo Associates Ltd. All rights reserved.
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July 20, 1989 NazCron V1.0 - Cron type event manager Page 9
each name */
if numwords > 0 then do
do j=1 to numwords
event = word(eventlist,j)
'SHOW_EVENT '|| event
if (rc = 0) then say 'Event: ' || event || ', ' || result
else say 'Event: ' || event || ' not found.'
end
end
end
Historical notes
----------------
A short while ago, I stumbled on and installed a copy of AmiCron
to help with unattended maintenance on our BBS, Viva! Amiga!
While AmiCron was serviceable, and did pretty much what we
wanted, there was the problem of it requiring a CLI window. With
the AmiCron window up 24 hours a day amidst lots of activity, it
was very easy to type a character into the window by mistake,
thus freezing AmiCron; it would simply stop working until I
noticed the stray characters and backspaced them out. This
problem, and my fumble fingers, led to too many missed events.
Since Rick Schaeffer and Christian Balzar, AmiCron authors, were
kind enough to include source with the package, I decided to
remove the CLI requirement by using the Lattice 5.0 startup
routine CBack.o. On perusing the source, I discovered other
things about AmiCron that, I felt, could be improved.
AmiCron woke up every minute, opened the CRONTAB file, read all
of the records to execute any commands that were due, closed the
file and went back to sleep. The process of sleeping for a
minute also required some unnecessary I/O. It would create a
message port, allocate an EXTIO block, open the timer device, go
to sleep, wake up, close the timer device, free the EXTIO block
and delete the message port. It went through all of these steps
every minute. With the thought to make improvements to some of
this code, I began to modify the source. I hadn't edited too
many lines before I realized that I really had to redesign the
thing to do what I wanted.
The timer routines have been simplified, eliminating the DoIO
which waited for the timer to complete. Instead NazCron does a
SendIO and the wait for timer completion occurs in a central loop
in "main". In fact, I lifted this code from a commercial program
we are developing. With this done, I was able to fold in Arexx
command handling so that the resulting program is an ARexx host.
The timer request is allocated once when the program starts so
that each minute the timer functions simply compute the next
Copyright 1989 by Don Nafis and Nazlo Associates Ltd. All rights reserved.
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July 20, 1989 NazCron V1.0 - Cron type event manager Page 10
timeout period and issue another SendIO.
A bigger change involves the actual handling of the events
themselves. NazCron reads the CRONTAB file on startup, loads the
events into Exec Node structures and chains them in a List. Each
time NazCron wakes up, it locks the current CRONTAB file,
examines the FileInfoBlock structure to determine, via timestamp,
if the file has changed since it was last loaded. If it has, all
events previously loaded from the CRONTAB file are deleted from
the list and the file is reread and loaded back into memory with
any changes that were made to the file. If the timestamp was not
changed, no more file accesses are necessary. The list is then
scanned for events to be executed.
Of course, ARexx handling was not present at all in the original
program. NazCron was my first attempt to make useful ARexx
functions available in a program. My initial design included a
small number of commands, but as I began programming, I couldn't
help but add virtually everything I could think of. It was easy
to do.
Surprisingly, with all of the new code for event list handling,
ARexx commands and new file I/O, the resulting program size is
about 1500 bytes SMALLER than the AmiCron program it replaces.
Most of the decrease is probably attributable to the fact that I
Amiga-tized it, the rest to the superb Lattice 5.0 optimization
algorithms. NazCron has no remaining traces of portability, so
don't expect to see it on your local GS or COCO real soon now.
Thanks to:
----------
Lattice for the great 5.0 package - especially CPR,
Bill Hawes for ARexx,
Eric Lavitsky for his well structured and information-packed
Amiga programming course,
Rick Schaeffer and Christian Balzar for the original AmiCron,
Jay Miner (and friends) for the Amiga and
My family for putting up with me programming while they baked
their brains out on the beach.
I wouldn't have written this program without you guys.
Copyright 1989 by Don Nafis and Nazlo Associates Ltd. All rights reserved.
c
