1 ## snooze: run a command at a particular time
3 `snooze` is a new tool for waiting until a particular time and then
4 running a command. Together with a service supervision system such as
5 runit, 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)
26 - ad-hoc usage possible, just run the program from command line
29 - less confusing usage (I hope)
30 - filtering by ISO week and day of year
34 - due to supervision, no centralized daemon required
35 - filtering by ISO week and day of year
39 * run five minutes after midnight, every day:
42 * run at 2:15pm on the first of every month:
44 snooze: `-d1 -H2 -M15`
45 * run at 10 pm on weekdays:
48 * run 23 minutes after midnight, 2am, 4am ..., everyday:
49 cron: `23 0-23/2 * * *`
51 * run every second week:
58 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...
60 * `-n`: dry-run, print the next 5 times the command would run.
61 * `-v`: verbose, print scheduled (and rescheduled) times.
62 * `-t`, `-T`: see below timefiles
63 * `-R`: add between 0 and RANDDELAY seconds to the scheduled time.
64 * `-s`: commands are executed even if they are SLACK (default: 60) seconds late.
66 The durations RANDDELAY and SLACK and TIMEWAIT are parsed as seconds,
67 unless a postfix of `m` for minutes, `h` for hours, or `d` for days is used.
69 The remaining arguments are patterns for the time fields:
73 * `-w`: weekday (0-7, sunday is 0 and 7)
75 * `-W`: ISO week of year (0..53)
80 The following syntax is used for these options:
82 * exact match: `-d 3`, run on the 3rd
83 * alternation: `-d 3,10,27`, run on 3rd, 10th, 27th
84 * range: `-d 1-5`, run on 1st, 2nd, 3rd, 4th, 5th
85 * star: `-d '*'`, run every day
86 * repetition: `-d /5`, run on 5th, 10th, 15th, 20th, 25th, 30th day
87 * shifted repetition: `-d 2/5`, run on 7th, 12th, 17th, 22nd, 27th day
89 and combinations of those, e.g. `-d 1-10,15/5,28`.
91 The defaults are `-d* -m* -w* -D* -W* -H0 -M0 -S0`, that is, every midnight.
93 Note that *all* patterns need to match (contrary to cron where either
94 day of month *or* day of week matches), so `-w5 -d13` only runs on
99 Optionally, you can keep track of runs in time files, using `-t` and
102 When `-T` is passed, execution will not start earlier than the mtime
103 of TIMEFILE plus TIMEWAIT seconds.
105 When `-T` is *not* passed, snooze will start finding the first matching time
106 starting from the mtime of TIMEFILE, and taking SLACK into account.
107 (E.g. `-H0 -s 1d -t timefile` will start an instant
108 execution when timefile has not been touched today, whereas without `-t`
109 this would always wait until next midnight.)
111 If TIMEFILE does not exist, it will be assumed outdated enough to
112 ensure earliest execution.
114 snooze does not update the timefiles, your job needs to do that!
115 Only mtime is looked at, so touch(1) is good.
119 * snooze parses the option flags and computes the first time the
120 date pattern matches, as a symbolic date
121 * if a timefile is specified, the time is upped to timefile + timewait seconds
122 * if a random delay is requested, it is added
123 * snooze computes how far this event is in the future
124 * snooze sleeps that long, but at most 5 minutes
125 * after waking, snooze recomputes how far the event is in the future
126 * if the event is in the past, but fewer than SLACK seconds, snooze
127 execs the command. You need to ensure (by setting up supervision)
128 snooze runs again after that!
129 * if we woke due to a SIGALRM, the command is executed immediately as well
130 * if the event is in the future, recompute the time it takes, possibly
131 considering shifting of the system time or timezone changes
132 (possibly only works on glibc)
133 * If no command was given, just return with status 0
138 Run a job like cron, every day at 7am and 7pm:
140 exec snooze -H7,19 rdumpfs / /data/dump/mybox 2>&1
142 Run a job daily, never twice a day:
144 exec snooze -H0 -s 1d -t timefile \
145 sh -c 'run-parts /etc/cron.daily; touch timefile'
147 Use snooze inline, run a mirror script every hour at 30 minutes past,
148 but ensure there are at least 20 minutes in between.
151 snooze -H'*' -M30 -t timefile -T 20m
152 touch timefile # remove this if instantly retrying on failure were ok
156 Use snooze inline, cron-style mail:
160 actualjob >output 2>&1 ||
161 mail -s "$(hostname): snooze job failed with status $?" root <output
163 Snooze for rate-limiting a general purpose runit service: don't
164 restart faster than every two minutes. (Note that after a crash with a
165 daemon runtime of more than two minutes, it will be restarted
169 snooze -H'*' -M'*' -S'*' -t timefile -T 2m
175 Use `make all` to build, `make install` to install relative to `PREFIX`
176 (`/usr/local` by default). The `DESTDIR` convention is respected.
177 You can also just copy the binary into your `PATH`.
181 snooze is in the public domain.
183 To the extent possible under law,
184 Christian Neukirchen <chneukirchen@gmail.com>
185 has waived all copyright and related or
186 neighboring rights to this work.
188 http://creativecommons.org/publicdomain/zero/1.0/