incubator-nuttx/tools/link.sh

#!/bin/bash
############################################################################
# tools/link.sh
#
#   Copyright (C) 2008 Gregory Nutt. All rights reserved.
#   Author: Gregory Nutt <gnutt@nuttx.org>
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in
#    the documentation and/or other materials provided with the
#    distribution.
# 3. Neither the name NuttX nor the names of its contributors may be
#    used to endorse or promote products derived from this software
#    without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
# COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
# OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.
#
############################################################################
#set -x

src=$1
dest=$2

# Verify that arguments were provided

if [ -z "${src}" -o -z "${dest}" ]; then
	echo "Missing src and/or dest arguments"
	exit 1
fi

# Check if something already exists at the destination path replace it with
# the new link (which might be different).  Note that we check for the
# the link (-h) before we check for existence (-e) because a bad link will
# report that it does not exist.

if [ -h "${dest}" ]; then

	# If the link is already created (and matches the request) do nothing

	if [ "$(readlink ${dest})" = "${src}" ]; then
		exit 0
	fi

	# Otherwise, remove the link

	rm -f "${dest}"
else

	# If the path exists and is a directory that contains the "fake link"
	# mark, then treat it like a soft link (i.e., remove the directory)

	if [ -d "${dest}" -a -f "${dest}/.fakelnk" ]; then
		rm -rf "${dest}"
	else

		# Does anything exist at the destination path?

		if [ -e "${dest}" ]; then

			# It is something else (like a file) or directory that does
			# not contain the "fake link" mark

			echo "${dest} already exists but is not a symbolic link"
			exit 1
		fi
	fi
fi

# Verify that a directory exists at the source path

if [ ! -d "${src}" ]; then
	echo "No directory at ${src}"
	exit 1
fi

# Create the soft link

ln -s "${src}" "${dest}" || \
	{ echo "Failed to create link: $dest" ; exit 1 ; }