1 ## snooze: run a command at a particular time
3 `snooze` is a new tool for to wait until a particular time and then
4 run a command. Together with a service supervision system such as runit,
5 this can be used to replace cron(8).
7 `lr` has been tested on Linux 4.2.
8 It will likely work on other Unix-like systems with C99.
14 - no overlapping job runs possible
15 - filtering by ISO week and day of year
16 - due to supervision, no centralized daemon required
17 - due to supervision, can easily disable jobs or force their
19 - due to supervision, have custom logs
20 - due to no centralized daemon, no fuzzing with multiple users/permissions
21 - very robust with respect to external time changes
22 - can use a file timestamp to ensure minimum waiting time between two
23 runs, even across reboots
24 - randomized delays (some cron have that)
25 - variable slack (no need for anacron)
28 - less confusing usage (I hope)
29 - filtering by ISO week and day of year
33 - due to supervision, no centralized daemon required
37 * run five minutes after midnight, every day:
40 * run at 2:15pm on the first of every month:
42 snooze: `-d1 -H2 -M15`
43 * run at 10 pm on weekdays:
46 * run 23 minutes after midnight, 2am, 4am ..., everyday:
47 cron: `23 0-23/2 * * *`
49 * run every second week:
56 snooze [-nv] [-t timefile] [-T timewait] [-R randdelay] [-s slack] [-d mday] [-m mon] [-w wday] [-D yday] [-W yweek] [-H hour] [-M min] [-S sec] COMMAND...
58 * `-n`: dry-run, print the next 5 times the command would run.
59 * `-v`: verbose, print scheduled (and rescheduled) times.
60 * `-t`, `-T`: see below timefiles
61 * `-R`: add between 0 and RANDDELAY seconds to the scheduled time.
62 * `-s`: commands are executed even if they are SLACK (default: 60) seconds late.
64 The remaining arguments are patterns for the time fields:
68 * `-w`: weekday (0-7, sunday is 0 and 7)
70 * `-W`: ISO week of year (0..53)
75 The following syntax is used for these options:
77 * exact match: `-d 3`, run on the 3rd
78 * alternation: `-d 3,10,27`, run on 3rd, 10th, 27th
79 * range: `-d 1-5`, run on 1st, 2nd, 3rd, 4th, 5th
80 * star: `-d '*'`, run every day
81 * repetition: `-d /5`, run on 5th, 10th, 15th, 20th, 25th, 30th day
82 * shifted repetition: `-d 2/5`, run on 7th, 12th, 17th, 22nd, 27th day
84 and combinations of those, e.g. `-d 1-10,15/5,28`.
86 The defaults are `-d* -m* -w* -D* -W* -H0 -M0 -S0`, that is, every midnight.
88 Note that *all* patterns need to match (contrary to cron where either
89 day of month *or* day of week matches), so `-w5 -d13` only runs on
94 Optionally, you can keep track of runs in time files, using `-t` and
97 When `-T` is passed, execution will not start earlier than the mtime
98 of TIMEFILE plus TIMEWAIT seconds.
100 When `-T` is *not* passed, snooze will start finding the first matching time
101 starting from the mtime of TIMEFILE, and taking SLACK into account.
102 (E.g. `-H0 -s$((24*60*60)) -t timefile` will start an instant
103 execution when timefile has not been touched today, whereas without `-t`
104 this would always wait until next midnight.)
106 If TIMEFILE does not exist, it will be assumed outdated enough to
107 ensure earliest execution.
109 snooze does not update the timefiles, your job needs to do that!
110 Only mtime is looked at, so touch(1) is good.
114 * snooze parses the option flags and computes the first time the
115 date pattern matches, as a symbolic date
116 * if a timefile is specified, the time is upped to timefile + timewait seconds
117 * if a random delay is requested, it is added
118 * snooze computes how far this event is in the future
119 * snooze sleeps that long, but at most 5 minutes
120 * after waking, snooze recomputes how far the event is in the future
121 * if the event is in the past, but fewer than SLACK seconds, snooze
122 execs the command. You need to ensure (by setting up supervision)
123 snooze runs again after that!
124 * if we woke due to a SIGALRM, the command is executed immediately as well
125 * if the event is in the future, recompute the time it takes, possibly
126 considering shifting of the system time or timezone changes
127 (possibly only works on glibc)
128 * If no command was given, just return with status 0
133 Run a job like cron, every day at 7am and 7pm:
135 exec snooze -H7,19 rdumpfs / /data/dump/mybox 2>&1
137 Run a job daily, never twice a day:
139 exec snooze -H0 -s $((24*60*60)) -t timefile \
140 sh -c 'run-parts /etc/cron.daily; touch timefile'
142 Use snooze inline, run a mirror script every hour at 30 minutes past,
143 but ensure there are at least 20 minutes in between.
146 snooze -H'*' -M30 -t timefile -T $((20*60))
147 touch timefile # remove this if instantly retrying on failure is ok
151 Use snooze inline, cron-style mail:
155 actualjob >output 2>&1 ||
156 mail -s "$(hostname): snooze job failed with status $?" root <output
160 Use `make all` to build, `make install` to install relative to `PREFIX`
161 (`/usr/local` by default). The `DESTDIR` convention is respected.
162 You can also just copy the binary into your `PATH`.
166 snooze is in the public domain.
168 To the extent possible under law,
169 Christian Neukirchen <chneukirchen@gmail.com>
170 has waived all copyright and related or
171 neighboring rights to this work.
173 http://creativecommons.org/publicdomain/zero/1.0/