Build system and directory structure cleanup

Signed-off-by: David Oberhollenzer <david.oberhollenzer@tele2.at>

8 files changed, 797 insertions, 1 deletions

diff --git a/cmd/Makemodule.am b/cmd/Makemodule.am
index 40c0933..f0ae3f9 100644
--- a/cmd/Makemodule.am
+++ b/cmd/Makemodule.am
@@ -15,5 +15,18 @@ killall5_CPPFLAGS = $(AM_CPPFLAGS)
 killall5_CFLAGS = $(AM_CFLAGS)
 killall5_LDFLAGS = $(AM_LDFLAGS)
 
-sbin_PROGRAMS += reboot shutdown
+SRVHEADERS = cmd/service/servicecmd.h
+
+service_SOURCES = cmd/service/servicecmd.c cmd/service/help.c
+service_SOURCES += cmd/service/enable.c cmd/service/disable.c
+service_SOURCES += cmd/service/dumpscript.c cmd/service/list.c
+service_SOURCES += $(SRVHEADERS)
+service_CPPFLAGS = $(AM_CPPFLAGS)
+service_CFLAGS = $(AM_CFLAGS)
+service_LDFLAGS = $(AM_LDFLAGS)
+service_LDADD = libinit.a
+
+EXTRA_DIST += $(SRVHEADERS)
+
+sbin_PROGRAMS += service reboot shutdown
 helper_PROGRAMS += killall5
diff --git a/cmd/service/disable.c b/cmd/service/disable.c
new file mode 100644
index 0000000..8a6f9f3
--- /dev/null
+++ b/cmd/service/disable.c
@@ -0,0 +1,89 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * Copyright (C) 2018 - David Oberhollenzer
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <stdio.h>
+#include <errno.h>
+
+#include "servicecmd.h"
+
+static int cmd_disable(int argc, char **argv)
+{
+	int ret = EXIT_FAILURE;
+	char *linkname, *ptr;
+	struct stat sb;
+
+	if (check_arguments(argv[0], argc, 2, 3))
+		return EXIT_FAILURE;
+
+	for (ptr = argv[1]; isalnum(*ptr) || *ptr == '_'; ++ptr)
+		;
+
+	if (*ptr != '\0') {
+		fprintf(stderr, "Invalid service name '%s'\n", argv[1]);
+		tell_read_help(argv[0]);
+		return EXIT_FAILURE;
+	}
+
+	if (argc == 3) {
+		ret = asprintf(&linkname, "%s/%s@%s",
+				SVCDIR, argv[1], argv[2]);
+	} else {
+		ret = asprintf(&linkname, "%s/%s", SVCDIR, argv[1]);
+	}
+
+	if (ret < 0) {
+		perror("asprintf");
+		return EXIT_FAILURE;
+	}
+
+	if (lstat(linkname, &sb)) {
+		fprintf(stderr, "lstat %s: %s\n", linkname, strerror(errno));
+		goto out;
+	}
+
+	if ((sb.st_mode & S_IFMT) != S_IFLNK) {
+		fprintf(stderr, "error: '%s' is not a symlink!", linkname);
+		goto out;
+	}
+
+	if (unlink(linkname)) {
+		fprintf(stderr, "removing %s: %s\n",
+			linkname, strerror(errno));
+		goto out;
+	}
+
+	ret = EXIT_SUCCESS;
+out:
+	free(linkname);
+	return ret;
+}
+
+static command_t disable = {
+	.cmd = "disable",
+	.usage = "<name> [argument]",
+	.s_desc = "disable a service",
+	.l_desc = "This disables a service by removing the coresponding "
+		  "symlink in " SVCDIR ".",
+	.run_cmd = cmd_disable,
+};
+
+REGISTER_COMMAND(disable)
diff --git a/cmd/service/dumpscript.c b/cmd/service/dumpscript.c
new file mode 100644
index 0000000..880631f
--- /dev/null
+++ b/cmd/service/dumpscript.c
@@ -0,0 +1,182 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * Copyright (C) 2018 - David Oberhollenzer
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+
+#include "servicecmd.h"
+#include "service.h"
+
+static service_t *try_load(const char *directory, const char *filename)
+{
+	int dirfd, type;
+	struct stat sb;
+	service_t *svc;
+
+	dirfd = open(directory, O_RDONLY | O_DIRECTORY);
+
+	if (dirfd < 0) {
+		perror(directory);
+		return NULL;
+	}
+
+	if (fstatat(dirfd, filename, &sb, AT_SYMLINK_NOFOLLOW)) {
+		fprintf(stderr, "stat %s/%s: %s\n",
+			directory, filename, strerror(errno));
+		close(dirfd);
+		return NULL;
+	}
+
+	type = (sb.st_mode & S_IFMT);
+
+	if (type != S_IFREG && type != S_IFLNK)
+		return NULL;
+
+	svc = rdsvc(dirfd, filename);
+	close(dirfd);
+	return svc;
+}
+
+enum {
+	NEED_QUOTES = 0x01,
+	NEED_ESCAPE = 0x02,
+};
+
+static int check_str(const char *str)
+{
+	int ret = 0;
+
+	while (*str != '\0') {
+		if (isspace(*str))
+			ret |= NEED_QUOTES;
+
+		if (!isascii(*str) || !isprint(*str))
+			ret |= NEED_ESCAPE | NEED_QUOTES;
+
+		if (*str == '\\' || *str == '"' || *str == '\n')
+			ret |= NEED_ESCAPE | NEED_QUOTES;
+
+		++str;
+	}
+
+	return ret;
+}
+
+static void print_str(const char *str)
+{
+	int flags = check_str(str);
+
+	if (flags & NEED_QUOTES)
+		fputc('"', stdout);
+
+	if (flags & NEED_ESCAPE) {
+		while (*str != '\0') {
+			switch (*str) {
+			case '\a': fputs("\\a", stdout); break;
+			case '\b': fputs("\\b", stdout); break;
+			case '\f': fputs("\\f", stdout); break;
+			case '\r': fputs("\\r", stdout); break;
+			case '\t': fputs("\\t", stdout); break;
+			case '\n': fputs("\\n", stdout); break;
+			case '\\':
+			case '"':
+				fprintf(stdout, "\\%c", *str);
+				break;
+			default:
+				if (!isascii(*str) || !isprint(*str)) {
+					fprintf(stdout, "\\x%02X", *str);
+				} else {
+					fputc(*str, stdout);
+				}
+				break;
+			}
+			++str;
+		}
+	} else {
+		fputs(str, stdout);
+	}
+
+	if (flags & NEED_QUOTES)
+		fputc('"', stdout);
+}
+
+static int cmd_dumpscript(int argc, char **argv)
+{
+	char *filename, *ptr;
+	service_t *svc;
+	size_t len;
+	exec_t *e;
+	int i;
+
+	if (check_arguments(argv[0], argc, 2, 3))
+		return EXIT_FAILURE;
+
+	for (len = 1, i = 1; i < argc; ++i)
+		len += strlen(argv[i]) + 1;
+
+	filename = alloca(len);
+	filename[0] = '\0';
+
+	for (i = 1; i < argc; ++i) {
+		if (i > 1)
+			strcat(filename, "@");
+		strcat(filename, argv[i]);
+	}
+
+	svc = try_load(SVCDIR, filename);
+
+	if (svc == NULL) {
+		fprintf(stderr, "Could not load service '%s'\n", filename);
+		return EXIT_FAILURE;
+	}
+
+	fprintf(stdout, "#\n# commands executed for serice '%s'\n#\n",
+		filename);
+
+	for (e = svc->exec; e != NULL; e = e->next) {
+		ptr = e->args;
+
+		for (i = 0; i < e->argc; ++i) {
+			if (i)
+				fputc(' ', stdout);
+
+			print_str(ptr);
+			ptr += strlen(ptr) + 1;
+		}
+		
+		putchar('\n');
+	}
+
+	delsvc(svc);
+	return EXIT_SUCCESS;
+}
+
+static command_t dumpscript = {
+	.cmd = "dumpscript",
+	.usage = "<name> [arguments]",
+	.s_desc = "print commands executed for a service",
+	.l_desc = "This parses a service file from " SVCDIR " and "
+		  "produces a pseudo-shell-script containing the "
+		  "exact commands after argument expansion that init "
+		  "runs when starting the service.",
+	.run_cmd = cmd_dumpscript,
+};
+
+REGISTER_COMMAND(dumpscript)
diff --git a/cmd/service/enable.c b/cmd/service/enable.c
new file mode 100644
index 0000000..5d4195e
--- /dev/null
+++ b/cmd/service/enable.c
@@ -0,0 +1,98 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * Copyright (C) 2018 - David Oberhollenzer
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <stdio.h>
+#include <errno.h>
+
+#include "servicecmd.h"
+
+static int cmd_enable(int argc, char **argv)
+{
+	char *target, *linkname, *ptr;
+	int ret = EXIT_FAILURE;
+	struct stat sb;
+
+	if (check_arguments(argv[0], argc, 2, 3))
+		return EXIT_FAILURE;
+
+	for (ptr = argv[1]; isalnum(*ptr) || *ptr == '_'; ++ptr)
+		;
+
+	if (*ptr != '\0') {
+		fprintf(stderr, "Invalid service name '%s'\n", argv[1]);
+		tell_read_help(argv[0]);
+		return EXIT_FAILURE;
+	}
+
+	if (asprintf(&target, "%s/%s", TEMPLATEDIR, argv[1]) < 0) {
+		perror("asprintf");
+		return EXIT_FAILURE;
+	}
+
+	if (stat(target, &sb)) {
+		fprintf(stderr, "%s: %s\n", target, strerror(errno));
+		goto out_tgt;
+	}
+
+	if ((sb.st_mode & S_IFMT) != S_IFREG) {
+		fprintf(stderr, "%s: must be a regular file\n", target);
+		goto out_tgt;
+	}
+
+	if (argc == 3) {
+		ret = asprintf(&linkname, "%s/%s@%s",
+				SVCDIR, argv[1], argv[2]);
+	} else {
+		ret = asprintf(&linkname, "%s/%s", SVCDIR, argv[1]);
+	}
+
+	if (ret < 0) {
+		perror("asprintf");
+		goto out_tgt;
+	}
+
+	if (symlink(target, linkname)) {
+		fprintf(stderr, "creating symlink '%s' -> '%s: %s\n",
+			linkname, target, strerror(errno));
+		goto out;
+	}
+
+	ret = EXIT_SUCCESS;
+out:
+	free(linkname);
+out_tgt:
+	free(target);
+	return ret;
+}
+
+static command_t enable = {
+	.cmd = "enable",
+	.usage = "<name> [argument]",
+	.s_desc = "enable a service",
+	.l_desc = "This marks a service as enabled by creating a symlink in "
+		  SVCDIR " pointing to the template file in " TEMPLATEDIR ". "
+		  "An optional argument can be supplied to parameterize the "
+		  "template.",
+	.run_cmd = cmd_enable,
+};
+
+REGISTER_COMMAND(enable)
diff --git a/cmd/service/help.c b/cmd/service/help.c
new file mode 100644
index 0000000..4fa9951
--- /dev/null
+++ b/cmd/service/help.c
@@ -0,0 +1,129 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * Copyright (C) 2018 - David Oberhollenzer
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+#include "servicecmd.h"
+
+extern char *__progname;
+
+static void pretty_print(const char *str, int padd, int len)
+{
+	int i, brk;
+next:
+	while (isspace(*str) && *str != '\n')
+		++str;
+
+	if (!(*str))
+		return;
+
+	if (*str == '\n') {
+		fputc('\n', stdout);
+		++str;
+		len = padd;
+		goto next;
+	}
+
+	for (i = 0, brk = 0; str[i]; ++i) {
+		if (str[i] == '<' || str[i] == '[')
+			++brk;
+		if (str[i] == '>' || str[i] == ']')
+			--brk;
+		if (!brk && isspace(str[i]))
+			break;
+	}
+
+	if ((len + i) < 80) {
+		fwrite(str, 1, i, stdout);
+		str += i;
+		len += i;
+
+		if ((len + 1) < 80) {
+			fputc(' ', stdout);
+			++len;
+			goto next;
+		}
+	}
+
+	printf("\n%*s", padd, "");
+	len = padd;
+	goto next;
+}
+
+static void print_cmd_usage(const char *cmd, const char *usage)
+{
+	int padd;
+
+	padd = printf("Usage: %s %s ", __progname, cmd);
+
+	if ((strlen(usage) + padd) < 80) {
+		fputs(usage, stdout);
+		return;
+	}
+
+	pretty_print(usage, padd, padd);
+}
+
+static int cmd_help(int argc, char **argv)
+{
+	const char *help;
+	command_t *cmd;
+
+	if (argc < 2)
+		usage(EXIT_SUCCESS);
+
+	if (argc > 2) {
+		fprintf(stderr, "Too many arguments\n\n"
+				"Usage: %s help <command>", __progname);
+		return EXIT_FAILURE;
+	}
+
+	for (cmd = commands; cmd != NULL; cmd = cmd->next) {
+		if (strcmp(cmd->cmd, argv[1]) != 0)
+			continue;
+
+		print_cmd_usage(cmd->cmd, cmd->usage);
+		fputs("\n\n", stdout);
+
+		help = cmd->l_desc ? cmd->l_desc : cmd->s_desc;
+
+		if (islower(*help)) {
+			fputc(toupper(*(help++)), stdout);
+			pretty_print(help, 0, 1);
+		} else {
+			pretty_print(help, 0, 0);
+		}
+
+		fputc('\n', stdout);
+		return EXIT_SUCCESS;
+	}
+
+	fprintf(stderr, "Unknown command '%s'\n\n"
+			"Try `%s help' for a list of available commands\n",
+			argv[1], __progname);
+	return EXIT_FAILURE;
+}
+
+static command_t help = {
+	.cmd = "help",
+	.usage = "<command>",
+	.s_desc = "print a help text for a command",
+	.l_desc = "Print a help text for a specified command. If no command "
+		"is specified, print a generic help text and a list of "
+		"available commands.",
+	.run_cmd = cmd_help,
+};
+
+REGISTER_COMMAND(help)
diff --git a/cmd/service/list.c b/cmd/service/list.c
new file mode 100644
index 0000000..b9e342a
--- /dev/null
+++ b/cmd/service/list.c
@@ -0,0 +1,102 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * Copyright (C) 2018 - David Oberhollenzer
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+#include "servicecmd.h"
+#include "service.h"
+#include "config.h"
+
+static void print_services(service_t *svc)
+{
+	const char *ptr;
+	int i;
+
+	for (; svc != NULL; svc = svc->next) {
+		printf("Name: %s\n", svc->name);
+		printf("\tDescrption: %s\n", svc->desc);
+		printf("\tType: %s\n", svc_type_to_string(svc->type));
+		printf("\tTarget: %s\n", svc_target_to_string(svc->target));
+
+		if (svc->type == SVC_RESPAWN && svc->rspwn_limit > 0)
+			printf("\tRespawn limit: %d\n", svc->rspwn_limit);
+
+		ptr = svc->before;
+		if (ptr != NULL && svc->num_before > 0) {
+			fputs("\tMust be run before:\n", stdout);
+
+			for (i = 0; i < svc->num_before; ++i) {
+				printf("\t\t%s\n", ptr);
+				ptr += strlen(ptr) + 1;
+			}
+		}
+
+		ptr = svc->after;
+		if (ptr != NULL && svc->num_after > 0) {
+			fputs("\tMust be run after:\n", stdout);
+
+			for (i = 0; i < svc->num_after; ++i) {
+				printf("\t\t%s\n", ptr);
+				ptr += strlen(ptr) + 1;
+			}
+		}
+	}
+}
+
+static int cmd_list(int argc, char **argv)
+{
+	int i, ret = EXIT_SUCCESS;
+	service_list_t list;
+
+	if (check_arguments(argv[0], argc, 1, 2))
+		return EXIT_FAILURE;
+
+	if (svcscan(SVCDIR, &list)) {
+		fprintf(stderr, "Error while reading services from %s\n",
+			SVCDIR);
+		ret = EXIT_FAILURE;
+	}
+
+	if (argc == 2) {
+		i = svc_target_from_string(argv[1]);
+
+		if (i == -1) {
+			fprintf(stderr, "Unknown target `%s'\n", argv[1]);
+			tell_read_help(argv[0]);
+			ret = EXIT_FAILURE;
+			goto out;
+		}
+
+		print_services(list.targets[i]);
+	} else {
+		for (i = 0; i < TGT_MAX; ++i)
+			print_services(list.targets[i]);
+	}
+out:
+	del_svc_list(&list);
+	return ret;
+}
+
+static command_t list = {
+	.cmd = "list",
+	.usage = "[target]",
+	.s_desc = "print a list of currently enabled services",
+	.l_desc = "Print a list of currently enabled services. If an "
+		  "optional target is specified, print services for this "
+		  "target.",
+	.run_cmd = cmd_list,
+};
+
+REGISTER_COMMAND(list)
diff --git a/cmd/service/servicecmd.c b/cmd/service/servicecmd.c
new file mode 100644
index 0000000..84e6a32
--- /dev/null
+++ b/cmd/service/servicecmd.c
@@ -0,0 +1,90 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * Copyright (C) 2018 - David Oberhollenzer
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+#include <stdlib.h>
+#include <stdio.h>
+
+#include "servicecmd.h"
+#include "service.h"
+#include "config.h"
+#include "util.h"
+
+
+command_t *commands;
+
+extern char *__progname;
+
+
+void usage(int status)
+{
+	FILE *stream = (status == EXIT_SUCCESS ? stdout : stderr);
+	int padd = 0, len;
+	command_t *cmd;
+
+	fprintf(stream, "usage: %s <command> [args...]\n\n"
+			"Available commands:\n\n", __progname);
+
+	for (cmd = commands; cmd != NULL; cmd = cmd->next) {
+		len = strlen(cmd->cmd);
+
+		padd = len > padd ? len : padd;
+	}
+
+	for (cmd = commands; cmd != NULL; cmd = cmd->next) {
+		fprintf(stream, "%*s - %s\n",
+			(int)padd + 1, cmd->cmd, cmd->s_desc);
+	}
+
+	fprintf(stream, "\nTry `%s help <command>' for more information "
+			"on a specific command\n", __progname);
+
+	exit(status);
+}
+
+void tell_read_help(const char *cmd)
+{
+	fprintf(stderr, "Try `%s help %s' for more information.\n",
+		__progname, cmd);
+}
+
+int check_arguments(const char *cmd, int argc, int minc, int maxc)
+{
+	if (argc >= minc && argc <= maxc)
+		return 0;
+
+	fprintf(stderr, "Too %s arguments for `%s'\n",
+			argc > maxc ? "many" : "few", cmd);
+	tell_read_help(cmd);
+	return -1;
+}
+
+int main(int argc, char **argv)
+{
+	command_t *cmd;
+
+	if (argc < 2)
+		usage(EXIT_SUCCESS);
+
+	for (cmd = commands; cmd != NULL; cmd = cmd->next) {
+		if (!strcmp(cmd->cmd, argv[1])) {
+			return cmd->run_cmd(argc - 1, argv + 1);
+		}
+	}
+
+	fprintf(stderr, "Unknown command '%s'\n\n", argv[1]);
+	usage(EXIT_FAILURE);
+}
diff --git a/cmd/service/servicecmd.h b/cmd/service/servicecmd.h
new file mode 100644
index 0000000..b839799
--- /dev/null
+++ b/cmd/service/servicecmd.h
@@ -0,0 +1,93 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * Copyright (C) 2018 - David Oberhollenzer
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+#ifndef SERVICECMD_H
+#define SERVICECMD_H
+
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <ctype.h>
+
+#include "util.h"
+
+/*
+	Describes a command that can be launched by passing its name as
+	second command line argument to the main() function (i.e. immediately
+	after the actual program name).
+
+	Short and long descriptions can be provided to print out help text.
+
+	The main() function calls into a callback in this structure to execute
+	the command.
+*/
+typedef struct command_t {
+	struct command_t *next;
+
+	const char *cmd;	/* command name */
+	const char *usage;	/* list of possible arguments */
+	const char *s_desc;	/* short description used by help */
+	const char *l_desc;	/* long description used by help */
+
+	/*
+		Semantics are the same as for main(). Called from main()
+		function with first argument (i.e. top level program name)
+		removed.
+	*/
+	int (*run_cmd)(int argc, char **argv);
+} command_t;
+
+/* Global list of available commands */
+extern command_t *commands;
+
+/*
+	Implemented in servicecmd.c. Prints program usage message and
+	terminates with the given exit status.
+*/
+void usage(int status) NORETURN;
+
+/*
+	Write a message to stderr that advises the user how to consult the
+	help text for a specific command.
+*/
+void tell_read_help(const char *cmd);
+
+/*
+	Check if the argument count is within specified bounds (minc and maxc
+	inclusive). If it is, return 0.
+
+	If it isn't, complain about a wrong number of arguments for a
+	command (cmd), tell the user to consult the help text and return -1.
+*/
+int check_arguments(const char *cmd, int argc, int minc, int maxc);
+
+/*
+	To implement a new command, add a global, static instance of a
+	command_t (or derived) structure to a C file and pass it to this
+	macro to have it automatically registered on program startup.
+*/
+#define REGISTER_COMMAND(cmd) \
+	static void __attribute__((constructor)) register_##cmd(void) \
+	{ \
+		command_t *c = (command_t *)&cmd; \
+		\
+		c->next = commands; \
+		commands = c; \
+	}
+
+#endif /* SERVICECMD_H */
+