openrc-run: Support standard input redirection too

OpenRC already supports redirecting standard output/error of services.
This patch adds support for redirecting standard input as well. I
encountered the lack of this feature while working on a user service for
a Wayland compositor status bar which reads status text to be displayed
from stdin. Input redirection allows me to connect this user services to
another user service providing the status text via a named pipe.

Note that input redirection is also supported by SystemD (and
potentially other service supervisors) through the `StandardInput=`
directive [1].

[1]: https://www.freedesktop.org/software/systemd/man/latest/systemd.exec.html#StandardInput=

Author: nmeum

man/openrc-run.8

@@ -158,18 +158,23 @@ use this to change the user id, and optionally group id,  before
 or
 .Xr supervise-daemon 8
 launches the daemon.
-.It Ar output_log
-This is the path to a file or named pipe where the standard output from
-the service will be redirected. If you are starting this service with
+.It Ar input_file
+This is the path to a file or named pipe to which the standard input of the
+service will be redirected to. If you are starting this service with
 .Xr start-stop-daemon 8 ,
 ,  you must set
 .Pa command_background
 to true. Keep in mind that this path will be inside the chroot if the
 .Pa chroot
-variable is set.
+variable is set. Contrary to output and error redirection, input redirection
+assumes that the file exists already.
+.It Ar output_log
+The same thing as
+.Pa input_file
+but for the standard output.
 .It Ar error_log
 The same thing as
-.Pa output_log
+.Pa input_file
 but for the standard error output.
 .It Ar output_logger
 This is a process which will be used to log the standard output from the

man/start-stop-daemon.8

@@ -143,6 +143,13 @@ on POSIX systems and, additionally, batch and idle on Linux. If
 is an integer, it is passed directly to pthread_setschedparam(3).
 .It Fl -scheduler-priority Ar priority
 Sets the priority parameter of the scheduling policy of the daemon. See sched(7) for details.
+.It Fl 0 , -stdin Ar file
+Redirect the standard input of the process to file when started with
+.Fl background .
+The file Must be an absolute pathname, but relative to the path
+optionally given with
+.Fl r , -chroot .
+The file can also be a named pipe. The file must exist, otherwise an error is emitted.
 .It Fl 1 , -stdout Ar logfile
 Redirect the standard output of the process to logfile when started with
 .Fl background .

man/supervise-daemon.8

@@ -50,6 +50,8 @@ servicename
 .Ar chrootpath
 .Fl u , -user
 .Ar user
+.Fl 0 , -stdin
+.Ar file
 .Fl 1 , -stdout
 .Ar logfile
 .Fl 2 , -stderr
@@ -154,11 +156,20 @@ process to communicate with is determined by the name of the service
 taken from the RC_SVCNAME environment variable.
 .It Fl u , -user Ar user
 Start the daemon as the specified user.
-.It Fl 1 , -stdout Ar logfile
-Redirect the standard output of the process to logfile.
+.It Fl 0 , -stdin Ar file
+Redirect the standard input of the process to file.
 Must be an absolute pathname, but relative to the path optionally given with
 .Fl r , -chroot .
-The logfile can also be a named pipe.
+The file can also be a named pipe. Input redirection assumes that the file
+exists already while output redirection via
+.Fl 1 , -stdout
+or
+.Fl 1 , -stderr
+creates it, if it doesn't.
+.It Fl 1 , -stdout Ar logfile
+The same thing as
+.Fl 0 , -stdin
+but with the standard output.
 .It Fl 2 , -stderr Ar logfile
 The same thing as
 .Fl 1 , -stdout

sh/start-stop-daemon.sh

@@ -45,6 +45,7 @@ ssd_start()
 		--exec $command \
 		${chroot:+--chroot} $chroot \
 		${directory:+--chdir} $directory \
+		${input_file+--stdin} $input_file \
 		${output_log+--stdout} $output_log \
 		${error_log+--stderr} $error_log \
 		${output_logger:+--stdout-logger \"$output_logger\"} \

sh/supervise-daemon.sh

@@ -28,6 +28,7 @@ supervise_start()
 		${retry:+--retry} $retry \
 		${directory:+--chdir} $directory  \
 		${chroot:+--chroot} $chroot \
+		${input_file+--stdin} $input_file \
 		${output_log+--stdout} ${output_log} \
 		${error_log+--stderr} $error_log \
 		${output_logger:+--stdout-logger \"$output_logger\"} \

src/start-stop-daemon/start-stop-daemon.c

@@ -94,7 +94,7 @@ enum {
 
 const char *applet = NULL;
 const char *extraopts = NULL;
-const char getoptstring[] = "I:KN:PR:Sa:bc:d:e:g:ik:mn:op:s:tu:r:w:x:1:2:3:4:" \
+const char getoptstring[] = "I:KN:PR:Sa:bc:d:e:g:ik:mn:op:s:tu:r:w:x:0:1:2:3:4:" \
 	getoptstring_COMMON;
 const struct option longopts[] = {
 	{ "capabilities", 1, NULL, LONGOPT_CAPABILITIES},
@@ -124,6 +124,7 @@ const struct option longopts[] = {
 	{ "chroot",       1, NULL, 'r'},
 	{ "wait",         1, NULL, 'w'},
 	{ "exec",         1, NULL, 'x'},
+	{ "stdin",        1, NULL, '0'},
 	{ "stdout",       1, NULL, '1'},
 	{ "stderr",       1, NULL, '2'},
 	{ "stdout-logger",1, NULL, '3'},
@@ -162,6 +163,7 @@ const char * const longopts_help[] = {
 	"Chroot to this directory",
 	"Milliseconds to wait for daemon start",
 	"Binary to start/stop",
+	"Redirect stdin to file",
 	"Redirect stdout to file",
 	"Redirect stderr to file",
 	"Redirect stdout to process",
@@ -318,6 +320,7 @@ int main(int argc, char **argv)
 	gid_t gid = 0;
 	char *home = NULL;
 	int tid = 0;
+	char *redirect_stdin = NULL;
 	char *redirect_stderr = NULL;
 	char *redirect_stdout = NULL;
 	char *stderr_process = NULL;
@@ -601,6 +604,10 @@ int main(int argc, char **argv)
 			exec = optarg;
 			break;
 
+		case '0':   /* --stdin /path/to/stdin.input-file */
+			redirect_stdin = optarg;
+			break;
+
 		case '1':   /* --stdout /path/to/stdout.lgfile */
 			redirect_stdout = optarg;
 			break;
@@ -1071,6 +1078,13 @@ int main(int argc, char **argv)
 		stdin_fd = devnull_fd;
 		stdout_fd = devnull_fd;
 		stderr_fd = devnull_fd;
+		if (redirect_stdin) {
+			if ((stdin_fd = open(redirect_stdin,
+				    O_RDONLY)) == -1)
+				eerrorx("%s: unable to open the input file"
+				    " for stdin `%s': %s",
+				    applet, redirect_stdin, strerror(errno));
+		}
 		if (redirect_stdout) {
 			if ((stdout_fd = open(redirect_stdout,
 				    O_WRONLY | O_CREAT | O_APPEND,

src/supervise-daemon/supervise-daemon.c

@@ -87,7 +87,7 @@ enum {
 
 const char *applet = NULL;
 const char *extraopts = NULL;
-const char getoptstring[] = "A:a:D:d:e:g:H:I:Kk:m:N:p:R:r:s:Su:1:2:3" \
+const char getoptstring[] = "A:a:D:d:e:g:H:I:Kk:m:N:p:R:r:s:Su:0:1:2:3" \
 	getoptstring_COMMON;
 const struct option longopts[] = {
 	{ "healthcheck-timer",        1, NULL, 'a'},
@@ -112,6 +112,7 @@ const struct option longopts[] = {
 	{ "signal",       1, NULL, 's'},
 	{ "start",        0, NULL, 'S'},
 	{ "user",         1, NULL, 'u'},
+	{ "stdin",        1, NULL, '0'},
 	{ "stdout",       1, NULL, '1'},
 	{ "stderr",       1, NULL, '2'},
 	{ "stdout-logger",1, NULL, LONGOPT_STDOUT_LOGGER},
@@ -143,6 +144,7 @@ const char * const longopts_help[] = {
 	"Send a signal to the daemon",
 	"Start daemon",
 	"Change the process user",
+	"Redirect stdin to file",
 	"Redirect stdout to file",
 	"Redirect stderr to file",
 	"Redirect stdout to process",
@@ -168,6 +170,7 @@ static int stdin_fd;
 static int stdout_fd;
 static int stderr_fd;
 static struct ready ready;
+static char *redirect_stdin = NULL;
 static char *redirect_stderr = NULL;
 static char *redirect_stdout = NULL;
 static char *stderr_process = NULL;
@@ -554,6 +557,13 @@ RC_NORETURN static void child_process(char *exec, char **argv)
 	stdin_fd = devnull_fd;
 	stdout_fd = devnull_fd;
 	stderr_fd = devnull_fd;
+	if (redirect_stdin) {
+		if ((stdin_fd = open(redirect_stdin,
+			    O_RDONLY)) == -1)
+			eerrorx("%s: unable to open the input file"
+			    " for stdin `%s': %s",
+			    applet, redirect_stdin, strerror(errno));
+	}
 	if (redirect_stdout) {
 		if ((stdout_fd = open(redirect_stdout,
 			    O_WRONLY | O_CREAT | O_APPEND,
@@ -1057,6 +1067,10 @@ int main(int argc, char **argv)
 		}
 		break;
 
+		case '0':   /* --stdin /path/to/stdin.input-file */
+			redirect_stdin = optarg;
+			break;
+
 		case '1':   /* --stdout /path/to/stdout.lgfile */
 			redirect_stdout = optarg;
 			break;