1. #!/bin/execlineb
2. #
3. # This is the turnstile s6-rc backend. It accepts the action as its first
4. # argument, which is either "ready", "run", or "stop". The backend can be
5. # written in any language, in this case the shebang is used to run it.
6. #
7. # It also serves as an example of how to implement such backend in a non
8. # shell language.
9. #
10. # Arguments for "ready":
11. #
12. # live:     the path to s6-rc's live dir; it is the string that is
13. #           written by dinit into ready_fd for the "run" part of the process
14. #
15. # Arguments for "run":
16. #
17. # ready_p:  path to named pipe (fifo) that should be poked with a string; this
18. #           will be passed to the "ready" script of the sequence as its sole
19. #           argument (here this is the path to s6-rc's live state directory)
20. # srvdir:   an internal directory that can be used by the service manager
21. #           for any purpose (usually to keep track of its state)
22. # confdir:  the path where turnstile's configuration data reside, used
23. #           to source the configuration file
24. #
25. # Arguments for "stop":
26. #
27. # pid:      the PID of the service manager to stop (gracefully); it should
28. #           terminate the services it's running and then stop itself
29. #
30. # How the script manages its configuration and so on is up to the script.
31. #
32. # Note that the script *must* exec the service manager directly, i.e. the
33. # service manager must fully replace the shell process for this to work.
34. #
35. # Copyright 2024 Carlos Eduardo <carana2099@gmail.com>
36. # License: BSD-2-Clause
37. #
38.  
39. importas -i directive 1
40. shift -n 1
41.  
42. case $directive {
43.         run {
44.                 # source additional arguments.
45.                 # two subsitution steps are needed because https://skarnet.org/lists/skaware/2049.html
46.                 multisubstitute {
47.                         importas -i __confdir 3
48.                         importas -i __home    HOME
49.                 }
50.                 envfile -I -- ${__confdir}/s6-rc.conf
51.  
52.                 # despite the above warning, we do want serial substitution on these, so we import it here, before the bigger multisubstitute.
53.                 multisubstitute {
54.                         importas -uD "${HOME}/.local/share/s6/compiled" compiled compileddir
55.                         importas -uD "${statedir}/s6-rc"                live     livestatedir
56.                         importas -uD "${statedir}/env"                  env      envdir
57.                 }
58.                 multisubstitute {
59.                         importas -i readyfifo 1
60.                         importas -i statedir 2
61.                         importas -i confdir 3
62.                         # not used directly, but might be useful for the config file
63.                         importas -Si HOME
64.                         importas -Si USER
65.                         importas -Si XDG_RUNTIME_DIR
66.                         importas -Si SHELL
67.                         importas -Si LOGNAME
68.                 }
69.  
70.                 # Initialize state directory.
71.                 # confdir/s6 should have the definition for a s6-svscan-log
72.                 # service that acts as the catch-all loger. See:
73.                 # /run/service/s6-svscan-log
74.                 # on a s6-linux-init powered machine for an example.
75.                 # It should also contain a .s6-svscan/SIGINT file with
76.                 # foreground { s6-rc -bDa } s6-svscanctl -t .
77.                 if { cp -a -- ${confdir}/s6 ${statedir}/service }
78.  
79.                 pipeline -dw -- {
80.                         if {
81.                                 forstdin -x0 _
82.                                         exit 0
83.                         }
84.                         if -nt {
85.                                 # Create envdir.
86.                                 if { mkdir -p -- ${env} }
87.                                 # Init service management layer.
88.                                 if { s6-rc-init -c $compiled -l $live -- ${statedir}/service }
89.                                 # Wait for logger to come up.
90.                                 redirfd -w 2 ${statedir}/service/s6-svscan-log/fifo
91.                                 # Print string for the ready step.
92.                                 redirfd -w 1 ${readyfifo}
93.                                 printf %s $live
94.                         }
95.                         # tell s6-svscan to give up if anything goes awry.
96.                         s6-svscanctl -t -- ${statedir}/service
97.                 }
98.                         # turn pipeline output into notification-fd.
99.                         fdmove -c 3 1
100.                         # backup stderr for catch-all logger
101.                         fdmove -c 4 2
102.                         # fifo trick
103.                         redirfd -wnb 2 ${statedir}/service/s6-svscan-log/fifo
104.                         fdmove -c 1 2
105.                         # avoid leaking script arguments
106.                         emptyenv -P
107.                         # export extra info for helper scripts
108.                         export SVDIR ${statedir}/service
109.                         export TURNSTILE_S6RC_LIVESTATE_DIR ${live}
110.                         s6-svscan -d 3 -X 4 -- ${statedir}/service
111.         }
112.         ready {
113.                 importas -i string 1
114.                 s6-rc -l $string -up change default
115.         }
116.         stop {
117.                 importas -i ! 1
118.                 # Using INT instead of TERM so the s6-rc -bDa change hook runs
119.                 kill -s INT $!
120.         }
121. }
122.         exit 32
123.