supervise-daemon: implement output_logger and error_logger.

[Higgs1]

Implements #644. Allows redirecting process stdout and stderr to another process, just like is already possible with start-stop-daemon. Also addresses #341 and #118.

Almost all of the code is copied directly from s-s-d (#127). I tried to follow your coding style as best I could, I read several previously accepted PRs, and I tried to keep the diff to a minimum.

This works correctly on my machine (Alpine, x86_64) and is currently hosting several of my public services. The stdout and stderr output is successfully redirected to syslog on another machine, which is then emailed to me sometimes.

I didn't copy over the short command arg variants (-3 and -4) because -3 conflicts with supervise-daemon's "--reexec" which doesn't exist in s-s-d. I can edit if you prefer something else.

As an example, here's a snippet from my /etc/init.d file(s):

#!/sbin/openrc-run

supervisor=supervise-daemon
output_logger="logger -et '${RC_SVCNAME}'"
error_logger="logger -et '${RC_SVCNAME}' -p3"

depend() {
	use logger
}

This forwards stdout and stderr to syslog. -p3 sets the priority level to error.

[tomalok]

Implements #644. Allows redirecting process stdin and stdout to another process, just like is already possible with start-stop-daemon. Also addresses #341 and #118.

pretty sure you mean stderr and stdout here, and elsewhere.

[Higgs1]

Thank you! I think I've fixed it now. That was such an embarrassing mistake.

[ncopa]

I wonder if would make sense to move ../start-stop-daemon/pipes.c to shared/pipes.c?

Suggested change

	['supervise-daemon.c', '../start-stop-daemon/pipes.c', misc_c, plugin_c, schedules_c, usage_c, version_h],
	['supervise-daemon.c', pipes_c, misc_c, plugin_c, schedules_c, usage_c, version_h],

[ncopa]

diff --git a/src/shared/meson.build b/src/shared/meson.build
index b80b242e..04c70fef 100644
--- a/src/shared/meson.build
+++ b/src/shared/meson.build
@@ -10,6 +10,10 @@ schedules_c = files([
   'schedules.c',
   ])
 
+pipes_c = files([
+  'pipes.c',
+  ])
+
 if selinux_dep.found()
   selinux_c = files([
     'selinux.c',
diff --git a/src/start-stop-daemon/pipes.c b/src/shared/pipes.c
similarity index 100%
rename from src/start-stop-daemon/pipes.c
rename to src/shared/pipes.c
diff --git a/src/start-stop-daemon/pipes.h b/src/shared/pipes.h
similarity index 100%
rename from src/start-stop-daemon/pipes.h
rename to src/shared/pipes.h
diff --git a/src/start-stop-daemon/meson.build b/src/start-stop-daemon/meson.build
index d363ff94..6cae791d 100644
--- a/src/start-stop-daemon/meson.build
+++ b/src/start-stop-daemon/meson.build
@@ -1,5 +1,5 @@
 executable('start-stop-daemon',
-  ['start-stop-daemon.c', 'pipes.c', misc_c, schedules_c,
+  ['start-stop-daemon.c', pipes_c, misc_c, schedules_c,
        selinux_c, usage_c, version_h],
   c_args : [cc_audit_flags, cc_branding_flags, cc_pam_flags, cc_cap_flags, cc_selinux_flags],
   link_with: [libeinfo, librc],

[Higgs1]

Hi @ncopa , I'm a big fan enjoyer of Alpine Linux.

I was originally trying to keep the PR to a minimum, but I agree that moving it to the "shared" directory makes a lot more sense. This is the first PR I've submitted to a project of uh... this caliber, so I'm still learning all the ins and outs. I've updated it with your suggestion, thank you!