supervise-daemon: implement output_logger and error_logger.

Allows redirecting process stdin and stdout to another process,
just like is already possible with start-stop-daemon.

Also added --stdout-logger and --stderr-logger to the man page.

man/supervise-daemon.8

@@ -158,6 +158,23 @@ The logfile can also be a named pipe.
 The same thing as
 .Fl 1 , -stdout
 but with the standard error output.
+.It Fl -stdout-logger Ar cmd
+Run cmd as a child process redirecting the standard output to the
+standard input of cmd when started with
+.Fl background .
+Cmd must be an absolute pathname, but relative to the path optionally given with
+.Fl r , -chroot .
+This process must be prepared to accept input on stdin and be able to
+log it or send it to another location.
+.It Fl -stderr-logger Ar cmd
+Run cmd as a child process and 
+Redirect the standard error of the process to the standard input of cmd
+when started with
+.Fl background .
+Cmd must be an absolute pathname, but relative to the path optionally given with
+.Fl r , -chroot .
+This process must be prepared to accept input on stdin and be able to
+log it or send it to another location.
 .It Fl -capabilities Ar cap-list
 Start the daemon with the listed inheritable, ambient and bounding capabilities.
 The format is the same as in cap_iab(3).

sh/supervise-daemon.sh

@@ -30,6 +30,8 @@ supervise_start()
 		${chroot:+--chroot} $chroot \
 		${output_log+--stdout} ${output_log} \
 		${error_log+--stderr} $error_log \
+		${output_logger:+--stdout-logger \"$output_logger\"} \
+		${error_logger:+--stderr-logger \"$error_logger\"} \
 		${pidfile:+--pidfile} $pidfile \
 		${respawn_delay:+--respawn-delay} $respawn_delay \
 		${respawn_max:+--respawn-max} $respawn_max \

src/supervise-daemon/meson.build

@@ -1,5 +1,5 @@
 executable('supervise-daemon',
-  ['supervise-daemon.c', misc_c, plugin_c, schedules_c, usage_c, version_h],
+  ['supervise-daemon.c', '../start-stop-daemon/pipes.c', misc_c, plugin_c, schedules_c, usage_c, version_h],
   c_args : [cc_branding_flags, cc_pam_flags, cc_cap_flags, cc_selinux_flags],
   link_with: [libeinfo, librc],
   dependencies: [dl_dep, pam_dep, cap_dep, util_dep, selinux_dep],

src/supervise-daemon/supervise-daemon.c

@@ -62,6 +62,7 @@ static struct pam_conv conv = { NULL, NULL};
 #include "queue.h"
 #include "rc.h"
 #include "misc.h"
+#include "../start-stop-daemon/pipes.h"
 #include "plugin.h"
 #include "schedules.h"
 #include "_usage.h"
@@ -79,6 +80,8 @@ enum {
   LONGOPT_OOM_SCORE_ADJ,
   LONGOPT_NO_NEW_PRIVS,
   LONGOPT_SECBITS,
+  LONGOPT_STDERR_LOGGER,
+  LONGOPT_STDOUT_LOGGER,
 };
 
 const char *applet = NULL;
@@ -110,6 +113,8 @@ const struct option longopts[] = {
 	{ "user",         1, NULL, 'u'},
 	{ "stdout",       1, NULL, '1'},
 	{ "stderr",       1, NULL, '2'},
+	{ "stdout-logger",1, NULL, LONGOPT_STDOUT_LOGGER},
+	{ "stderr-logger",1, NULL, LONGOPT_STDERR_LOGGER},
 	{ "reexec",       0, NULL, '3'},
 	longopts_COMMON
 };
@@ -138,6 +143,8 @@ const char * const longopts_help[] = {
 	"Change the process user",
 	"Redirect stdout to file",
 	"Redirect stderr to file",
+	"Redirect stdout to process",
+	"Redirect stderr to process",
 	"reexec (used internally)",
 	longopts_help_COMMON
 };
@@ -160,6 +167,8 @@ static int stdout_fd;
 static int stderr_fd;
 static char *redirect_stderr = NULL;
 static char *redirect_stdout = NULL;
+static char *stderr_process = NULL;
+static char *stdout_process = NULL;
 #ifdef TIOCNOTTY
 static int tty_fd = -1;
 #endif
@@ -549,6 +558,12 @@ RC_NORETURN static void child_process(char *exec, char **argv)
 			eerrorx("%s: unable to open the logfile"
 				    " for stdout `%s': %s",
 				    applet, redirect_stdout, strerror(errno));
+	} else if (stdout_process) {
+		stdout_fd = rc_pipe_command(stdout_process);
+		if (stdout_fd == -1)
+			eerrorx("%s: unable to open the logging process"
+			    " for stdout `%s': %s",
+			    applet, stdout_process, strerror(errno));
 	}
 	if (redirect_stderr) {
 		if ((stderr_fd = open(redirect_stderr,
@@ -557,6 +572,12 @@ RC_NORETURN static void child_process(char *exec, char **argv)
 			eerrorx("%s: unable to open the logfile"
 			    " for stderr `%s': %s",
 			    applet, redirect_stderr, strerror(errno));
+	} else if (stderr_process) {
+		stderr_fd = rc_pipe_command(stderr_process);
+		if (stderr_fd == -1)
+			eerrorx("%s: unable to open the logging process"
+			    " for stderr `%s': %s",
+			    applet, stderr_process, strerror(errno));
 	}
 
 	dup2(stdin_fd, STDIN_FILENO);
@@ -1039,6 +1060,14 @@ int main(int argc, char **argv)
 			reexec = true;
 			break;
 
+		case LONGOPT_STDOUT_LOGGER:   /* --stdout-logger "command to run for stdout logging" */
+			stdout_process = optarg;
+			break;
+
+		case LONGOPT_STDERR_LOGGER:  /* --stderr-logger "command to run for stderr logging" */
+			stderr_process = optarg;
+			break;
+
 		case_RC_COMMON_GETOPT
 		}