skeleton-custom: use a script to check merged usr structure

Introduce support/scripts/check-merged-usr.sh, a script that check if a
given path complies to the merged /usr requirements:

    /
    /bin -> usr/bin
    /lib -> usr/lib
    /sbin -> usr/sbin
    /usr/bin/
    /usr/lib/
    /usr/sbin/

Use this script in skeleton-custom.mk instead of a bunch of variables
filled by $(shell ...) macros. The same script will be used to check
rootfs overlays, in a forthcoming change.

Signed-off-by: Carlos Santos <casantos@datacom.ind.br>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

1 files changed, 39 insertions, 0 deletions

diff --git a/support/scripts/check-merged-usr.sh b/support/scripts/check-merged-usr.sh
new file mode 100755
index 0000000000..433857cd8c
--- /dev/null
+++ b/support/scripts/check-merged-usr.sh
@@ -0,0 +1,39 @@
+#!/bin/sh
+#
+# Check if a given custom skeleton or overlay complies to the merged /usr
+# requirements:
+# /
+# /bin -> usr/bin
+# /lib -> usr/lib
+# /sbin -> usr/sbin
+# /usr/bin/
+# /usr/lib/
+# /usr/sbin/
+#
+# Output: the list of non-compliant paths (empty if compliant).
+#
+
+# Extract the inode numbers for all of those directories. In case any is
+# a symlink, we want to get the inode of the pointed-to directory, so we
+# append '/.' to be sure we get the target directory. Since the symlinks
+# can be anyway (/bin -> /usr/bin or /usr/bin -> /bin), we do that for
+# all of them.
+#
+lib_inode=$(stat -c '%i' "${1}/lib/." 2>/dev/null)
+bin_inode=$(stat -c '%i' "${1}/bin/." 2>/dev/null)
+sbin_inode=$(stat -c '%i' "${1}/sbin/." 2>/dev/null)
+usr_lib_inode=$(stat -c '%i' "${1}/usr/lib/." 2>/dev/null)
+usr_bin_inode=$(stat -c '%i' "${1}/usr/bin/." 2>/dev/null)
+usr_sbin_inode=$(stat -c '%i' "${1}/usr/sbin/." 2>/dev/null)
+
+not_merged_dirs=""
+test -z "$lib_inode" || \
+	test "$lib_inode" = "$usr_lib_inode" || \
+		not_merged_dirs="/lib"
+test -z "$bin_inode" || \
+	test "$bin_inode" = "$usr_bin_inode" || \
+		not_merged_dirs="$not_merged_dirs /bin"
+test -z "$sbin_inode" || \
+	test "$sbin_inode" = "$usr_sbin_inode" || \
+		not_merged_dirs="$not_merged_dirs /sbin"
+echo "${not_merged_dirs# }"