1cron(n) cron cron(n)
2______________________________________________________________________________
6
8 cron - Tool for automating the period callback of commands
9
11 package require Tcl 8.6
12 package require cron ?2.1?
14 ::cron::at ?processname? timecode command
16 ::cron::cancel processname
18 ::cron::every processname frequency command
20 ::cron::in ?processname? timecode command
22 ::cron::object_coroutine object coroutine ?info?
24 ::cron::sleep milliseconds
26 ::cron::task delete process
28 ::cron::task exists process
30 ::cron::task info process
32 ::cron::task set process field value ?field...? ?value...?
34 ::cron::wake ?who?
36 ::cron::clock_step milliseconds
38 ::cron::clock_delay milliseconds
40 ::cron::clock_sleep seconds ?offset?
42 ::cron::clock_set newtime
44______________________________________________________________________________
46
48 The cron package provides a Pure-tcl set of tools to allow programs to
49 schedule tasks to occur at regular intervals. Rather than force each
50 task to issue it's own call to the event loop, the cron system mimics
51 the cron utility in Unix: on task periodically checks to see if some‐
52 thing is to be done, and issues all commands for a given time step at
53 once.
54 Changes in version 2.0
56 While cron was originally designed to handle time scales > 1 second,
58 the latest version's internal understand time granularity down to the
59 millisecond, making it easier to integrate with other timed events.
60 Version 2.0 also understands how to properly integrate coroutines and
61 objects. It also adds a facility for an external (or script driven)
62 clock. Note that vwait style events won't work very well with an exter‐
63 nal clock.
64
66 ::cron::at ?processname? timecode command
67 This command registers a command to be called at the time speci‐
68 fied by timecode. If timecode is expressed as an integer, the
69 timecode is assumed to be in unixtime. All other inputs will be
70 interpreted by clock scan and converted to unix time. This task
71 can be modified by subsequent calls to this package's commands
72 by referencing processname. If processname exists, it will be
73 replaced. If processname is not given, one is generated and re‐
74 turned by the command.
75 ::cron::at start_coffee {Tomorrow at 9:00am} {remote::exec::coffeepot power on}
78 ::cron::at shutdown_coffee {Tomorrow at 12:00pm} {remote::exec::coffeepot power off}
79 ::cron::cancel processname
82 This command unregisters the process processname and cancels any
83 pending commands. Note: processname can be a process created by
84 either ::cron::at or ::cron::every.
85 ::cron::cancel check_mail
88 ::cron::every processname frequency command
91 This command registers a command to be called at the interval of
92 frequency. frequency is given in seconds. This task can be mod‐
93 ified by subsequent calls to this package's commands by refer‐
94 encing processname. If processname exists, it will be replaced.
95 ::cron::every check_mail 900 ::imap_client::check_mail
98 ::cron::every backup_db 3600 {::backup_procedure ::mydb}
99 ::cron::in ?processname? timecode command
102 This command registers a command to be called after a delay of
103 time specified by timecode. timecode is expressed as an sec‐
104 onds. This task can be modified by subsequent calls to this
105 package's commands by referencing processname. If processname
106 exists, it will be replaced. If processname is not given, one
107 is generated and returned by the command.
108 ::cron::object_coroutine object coroutine ?info?
110 This command registers a coroutine, associated with object to be
111 called given the parameters of info. If now parameters are
112 given, the coroutine is assumed to be an idle task which will
113 self-terminate. info can be given in any form compadible with
114 ::cron::task set
115 ::cron::sleep milliseconds
117 When run within a coroutine, this command will register the
118 coroutine for a callback at the appointed time, and immediately
119 yield.
120 If the ::cron::time variable is > 0 this command will advance
122 the internal time, 100ms at a time.
123 In all other cases this command will generate a fictious vari‐
125 able, generate an after call, and vwait the variable:
126 set eventid [incr ::cron::eventcount]
129 set var ::cron::event_#$eventid
130 set $var 0
131 ::after $ms "set $var 1"
132 ::vwait $var
133 ::unset $var
134 Usage:
137 ::cron::sleep 250
140 ::cron::task delete process
143 Delete the process specified the process
144 ::cron::task exists process
146 Returns true if process is registered with cron.
147 ::cron::task info process
149 Returns a dict describing process. See ::cron::task set for a
150 description of the options.
151 ::cron::task set process field value ?field...? ?value...?
153 If process does not exist, it is created. Options Include:
155 command
157 If coroutine is black, a global command which implements
158 this process. If coroutine is not black, the command to
159 invoke to create or recreate the coroutine.
160 coroutine
162 The name of the coroutine (if any) which implements this
163 process.
164 frequency
166 If -1, this process is terminated after the next event.
167 If 0 this process should be called during every idle
168 event. If positive, this process should generate events
169 periodically. The frequency is an integer number of mil‐
170 liseconds between events.
171 object The object associated with this process or coroutine.
173 scheduled
175 If non-zero, the absolute time from the epoch (in mil‐
176 liseconds) that this process will trigger an event. If
177 zero, and the frequency is also zero, this process is
178 called every idle loop.
179 running
181 A boolean flag. If true it indicates the process never
182 returned or yielded during the event loop, and will not
183 be called again until it does so.
184 ::cron::wake ?who?
186 Wake up cron, and arrange for its event loop to be run during
187 the next Idle cycle.
188 ::cron::wake {I just did something important}
191 Several utility commands are provided that are used internally within
194 cron and for testing cron, but may or may not be useful in the general
195 cases.
196 ::cron::clock_step milliseconds
198 Return a clock time absolute to the epoch which falls on the
200 next border between one second and the next for the value of
201 milliseconds
202 ::cron::clock_delay milliseconds
204 Return a clock time absolute to the epoch which falls on the
206 next border between one second and the next milliseconds in the
207 future.
208 ::cron::clock_sleep seconds ?offset?
210 Return a clock time absolute to the epoch which falls exactly
212 seconds in the future. If offset is given it may be positive or
213 negative, and will shift the final time to before or after the
214 second would flip.
215 ::cron::clock_set newtime
217 Sets the internal clock for cron. This command will advance the
219 time in 100ms increment, triggering events, until the internal
220 time catches up with newtime.
221 newtime is expressed in absolute milliseconds since the begin‐
223 ning of the epoch.
224
226 This document, and the package it describes, will undoubtedly contain
227 bugs and other problems. Please report such in the category odie of
228 the Tcllib Trackers [http://core.tcl.tk/tcllib/reportlist]. Please
229 also report any ideas for enhancements you may have for either package
230 and/or documentation.
231 When proposing code changes, please provide unified diffs, i.e the out‐
233 put of diff -u.
234 Note further that attachments are strongly preferred over inlined
236 patches. Attachments can be made by going to the Edit form of the
237 ticket immediately after its creation, and then using the left-most
238 button in the secondary navigation bar.
239
241 cron, odie
242
244 System
245
247 Copyright (c) 2016-2018 Sean Woods <yoda@etoyoc.com>
248tcllib 2.1 cron(n)