introduce lxc_config

It's a tiny program (exported through the api) wrapping the util.c
helpers for reading /etc/lxc/lxc.conf variables, and replaces
the kludgy shell duplication in lxc.functions.in

Changelog: Apr 30: address feedback from Dwight
	(exit error on failure, and use 'lxcpath' as name, not
	'default_path').

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Acked-by: Dwight Engen <dwight.engen@oracle.com>

src/lxc/Makefile.am

@@ -162,7 +162,8 @@ bin_PROGRAMS = \
 	lxc-unfreeze \
 	lxc-checkpoint \
 	lxc-restart \
-	lxc-kill
+	lxc-kill \
+	lxc-config
 
 pkglibexec_PROGRAMS = \
 	lxc-init
@@ -179,6 +180,7 @@ LDADD=liblxc.so @CAP_LIBS@ @APPARMOR_LIBS@ @SECCOMP_LIBS@
 lxc_attach_SOURCES = lxc_attach.c
 lxc_cgroup_SOURCES = lxc_cgroup.c
 lxc_checkpoint_SOURCES = lxc_checkpoint.c
+lxc_config_SOURCES = lxc_config.c
 lxc_console_SOURCES = lxc_console.c
 lxc_execute_SOURCES = lxc_execute.c
 lxc_freeze_SOURCES = lxc_freeze.c

src/lxc/lxc.functions.in

@@ -25,33 +25,6 @@ bindir=@BINDIR@
 templatedir=@LXCTEMPLATEDIR@
 lxcinitdir=@LXCINITDIR@
 
-get_default_lxcpath() {
+lxc_path=`lxc-config default_path`
-	LXC_PATH=$(grep -v "^#" "$globalconf" 2>/dev/null | grep "[ \t]*lxcpath[ \t]*=") || true
+lxc_vg=`lxc-config lvm_vg`
-	if [ -n "$LXC_PATH" ]; then
+lxc_zfsroot=`lxc-config zfsroot`
-		echo $LXC_PATH | awk -F= '{ print $2 }'
-	else
-		echo @LXCPATH@
-	fi
-}
-
-get_default_vg() {
-	LXC_VG=$(grep -v "^#" "$globalconf" 2>/dev/null | grep "[ \t]*lvm_vg[ \t]*=") || true
-	if [ -n "$LXC_VG" ]; then
-		echo $LXC_VG | awk -F= '{ print $2 }'
-	else
-		echo "lxc"
-	fi
-}
-
-get_default_zfsroot() {
-	LXC_ZFSROOT=$(grep -v "^#" "$globalconf" 2>/dev/null | grep "[ \t]*zfsroot[ \t]*=") || true
-	if [ -n "$LXC_ZFSROOT" ]; then
-		echo $LXC_ZFSROOT | awk -F= '{ print $2 }'
-	else
-		echo "tank/lxc"
-	fi
-}
-
-lxc_path=`get_default_lxcpath`
-lxc_vg=`get_default_vg`
-lxc_zfsroot=`get_default_zfsroot`

src/lxc/lxc_config.c

@@ -0,0 +1,50 @@
+#include <stdio.h>
+#include "config.h"
+#include "lxccontainer.h"
+
+struct lxc_config_items {
+	char *name;
+	const char *(*fn)(void);
+};
+
+struct lxc_config_items items[] =
+{
+	{ .name = "lxcpath", .fn = &lxc_get_default_config_path, },
+	{ .name = "lvm_vg", .fn = &lxc_get_default_lvm_vg, },
+	{ .name = "zfsroot", .fn = &lxc_get_default_zfs_root, },
+	{ .name = NULL, },
+};
+
+void usage(char *me)
+{
+	printf("Usage: %s -l: list all available configuration items\n", me);
+	printf("       %s item: print configuration item\n", me);
+	exit(1);
+}
+
+void list_config_items(void)
+{
+	struct lxc_config_items *i;
+
+	for (i = &items[0]; i->name; i++)
+		printf("%s\n", i->name);
+	exit(0);
+}
+
+int main(int argc, char *argv[])
+{
+	struct lxc_config_items *i;
+
+	if (argc < 2)
+		usage(argv[0]);
+	if (strcmp(argv[1], "-l") == 0)
+		list_config_items();
+	for (i = &items[0]; i->name; i++) {
+		if (strcmp(argv[1], i->name) == 0) {
+			printf("%s\n", i->fn());
+			exit(0);
+		}
+	}
+	printf("Unknown configuration item: %s\n", argv[1]);
+	exit(-1);
+}

src/lxc/lxccontainer.c

@@ -1009,6 +1009,16 @@ const char *lxc_get_default_config_path(void)
 	return default_lxc_path();
 }
 
+const char *lxc_get_default_lvm_vg(void)
+{
+	return default_lvm_vg();
+}
+
+const char *lxc_get_default_zfs_root(void)
+{
+	return default_zfs_root();
+}
+
 const char *lxc_get_version(void)
 {
 	return lxc_version();

src/lxc/lxccontainer.h

@@ -122,6 +122,8 @@ int lxc_container_get(struct lxc_container *c);
 int lxc_container_put(struct lxc_container *c);
 int lxc_get_wait_states(const char **states);
 const char *lxc_get_default_config_path(void);
+const char *lxc_get_default_lvm_vg(void);
+const char *lxc_get_default_zfs_root(void);
 const char *lxc_get_version(void);
 
 #if 0