Fix #71: Add support for enabling/disabling services in /etc/finit.d

This patch adds support for enabling and disabling services in
/etc/finit.d/ by adding another subdirectory:

    /etc/finit.d/available

Enabled service/run/task stanzas are by convention symlinked
to the parent dir.  The initctl tool has three new convenience
commands to facilitate operating with this:

   initctl list
   initctl enable  <CONF>
   initctl disable <CONF>

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

src/serv.c

@@ -0,0 +1,163 @@
+/* List and enable/disable service configurations
+ *
+ * Copyright (c) 2017  Joachim Nilsson <troglobit@gmail.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "config.h"
+
+#include <err.h>
+#include <glob.h>
+#include <stdio.h>
+#include <lite/lite.h>
+
+#define SCREEN_WIDTH 80		/* Calculate screen width as well, later */
+
+static const char *cwd;
+static const char *available = FINIT_RCSD "/available";
+static const char *enabled   = FINIT_RCSD "/enabled";
+
+static void pushd(const char *dir)
+{
+	cwd = get_current_dir_name();
+	chdir(dir);
+}
+
+static void popd(void)
+{
+	chdir(cwd);
+}
+
+static int calc_width(char *arr[], size_t len)
+{
+	int width = 0;
+	size_t i;
+
+	for (i = 0; i < len; i++) {
+		int w = strlen(arr[i]);
+
+		if (w > width)
+			width = w;
+	}
+
+	return width;
+}
+
+static void do_list(const char *heading, const char *path)
+{
+	int num;
+	int width;
+	size_t i;
+	glob_t gl;
+	char h[SCREEN_WIDTH] = "===============================================================================";
+
+	pushd(path);
+	if (glob("*.conf", 0, NULL, &gl)) {
+		chdir(cwd);
+		return;
+	}
+
+	if (gl.gl_pathc <= 0)
+		goto done;
+
+	num = snprintf(h, sizeof(h) - 1, "%s", path);
+	h[num] = ' ';
+	puts(h);
+
+	width = calc_width(gl.gl_pathv, gl.gl_pathc);
+	num = SCREEN_WIDTH / width;
+	if ((num - 1) * 2 + num * width > SCREEN_WIDTH)
+		num--;
+
+	for (i = 0; i < gl.gl_pathc; i++) {
+		if (i > 0 && !(i % num))
+			puts("");
+
+		printf("%-*s  ", width, gl.gl_pathv[i]);
+	}
+	puts("\n");
+
+done:
+	globfree(&gl);
+	popd();
+}
+
+int serv_list(char *arg)
+{
+	if (fisdir(available))
+		do_list("Available", available);
+	if (fisdir(enabled))
+		do_list("Enabled", enabled);
+	else if (fisdir(FINIT_RCSD))
+		do_list("Always enabled", FINIT_RCSD);
+
+	return 0;
+}
+
+int serv_enable(char *arg)
+{
+	char corr[40];
+	char link[80];
+	char path[80];
+
+	if (!strstr(arg, ".conf")) {
+		snprintf(corr, sizeof(corr), "%s.conf", arg);
+		arg = corr;
+	}
+
+	pushd(FINIT_RCSD);
+	snprintf(path, sizeof(path), "available/%s", arg);
+	if (!fexist(path))
+		errx(1, "Cannot find %s", path);
+
+	snprintf(link, sizeof(link), "%s/%s", FINIT_RCSD, arg);
+	if (fexist(link))
+		errx(1, "%s already exists", link);
+
+	return symlink(path, link) != 0;
+}
+
+int serv_disable(char *arg)
+{
+	char corr[40];
+	char link[80];
+	struct stat st;
+
+	if (!strstr(arg, ".conf")) {
+		snprintf(corr, sizeof(corr), "%s.conf", arg);
+		arg = corr;
+	}
+
+	snprintf(link, sizeof(link), "%s/%s", FINIT_RCSD, arg);
+	if (stat(link, &st))
+		err(1, "Cannot find %s", link);
+
+	if ((st.st_mode & S_IFMT) == S_IFLNK)
+		errx(1, "%s is not a symlink, move manually to %s first", link, available);
+
+	return remove(link) != 0;
+}
+
+/**
+ * Local Variables:
+ *  indent-tabs-mode: t
+ *  c-file-style: "linux"
+ * End:
+ */