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#!/bin/bash
#
# Copyright 2016 The Bazel Authors. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
set -euo pipefail
# Print the resolved path of a symbolic link (or the path itself if not a link).
#
# The result may be relative to the current working directory and may contain
# "." and ".." references. Use `normalize_path` to remove those.
#
# Fail and print nothing if the input path doesn't exist, i.e. it's a
# non-existent file, dangling symlink, or circular symlink.
function resolve_links() {
local name="$1"
if [ -e "$name" ]; then
# resolve all links, keep path absolute
while [ -L "$name" ]; do
local target=$(readlink "$name")
if [ "$(echo "$target" | head -c1)" = "/" ]; then
name="$target"
else
name="$(dirname "$name")/$target"
fi
done
echo "$name"
else
false # fail the function
fi
}
# Normalize a path string by removing "." and ".." references from it.
#
# Print the result to stdout.
#
# The path doesn't have to point to an existing file.
function normalize_path() {
local name="$1"
local path=""
local uplevels=0
while [ "$name" != "/" -a "$name" != "." ]; do
local segment="$(basename "$name")"
name="$(dirname "$name")"
[ "$segment" = "." ] && continue
if [ "$segment" = ".." ]; then
uplevels="$((${uplevels}+1))"
else
if [ "$uplevels" -gt 0 ]; then
uplevels="$((${uplevels}-1))"
else
path="${segment}/${path}"
fi
fi
done
if [ "$name" = "." ]; then
while [ "$uplevels" -gt 0 ]; do
path="../$path"
uplevels="$((${uplevels}-1))"
done
fi
path="${path%/}"
if [ "$name" = "/" ]; then
echo "/$path"
else
[ -n "$path" ] && echo "$path" || echo "."
fi
}
# Custom implementation of `realpath(1)`.
#
# Resolves a symlink to the absolute path it points to. Fails if the link or
# its target does not exist.
#
# Fails and prints nothing if the input path doesn't exist, i.e. it's a
# non-existent file, dangling symlink, or circular symlink.
#
# We use this method instead of `realpath(1)` because the latter is not
# available on Mac OS X by default.
function get_real_path() {
local name="$1"
name="$(resolve_links "$name" || echo)"
if [ -n "$name" ]; then
normalize_path "$(pwd)/$name"
else
false # fail the function
fi
}
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