使用Bash将绝对路径转换为给定当前目录的相对路径

例：

absolute="/foo/bar"
current="/foo/baz/foo"

# Magic

relative="../../bar"

如何创建魔术（希望不要太复杂的代码...）？

---

$ python -c "import os.path; print os.path.relpath('/foo/bar', '/foo/baz/foo')"

得到：

../../bar

---

使用来自GNU coreutils 8.23的realpath是最简单的，我认为：

$ realpath --relative-to="$file1" "$file2"

例如：

$ realpath --relative-to=/usr/bin/nmap /tmp/testing
../../../tmp/testing

---

这是对@pini目前最好评级解决方案进行了修正，功能完善的改进（可悲的是，它只处理少数案例）

提醒：'-z'测试字符串是否为零（=空），'-n'测试字符串是否为空。

# both $1 and $2 are absolute paths beginning with /
# returns relative path to $2/$target from $1/$source
source=$1
target=$2

common_part=$source # for now
result="" # for now

while [[ "${target#$common_part}" == "${target}" ]]; do
    # no match, means that candidate common part is not correct
    # go up one level (reduce common part)
    common_part="$(dirname $common_part)"
    # and record that we went back, with correct / handling
    if [[ -z $result ]]; then
        result=".."
    else
        result="../$result"
    fi
done

if [[ $common_part == "/" ]]; then
    # special case for root (no common path)
    result="$result/"
fi

# since we now have identified the common part,
# compute the non-common part
forward_part="${target#$common_part}"

# and now stick all parts together
if [[ -n $result ]] && [[ -n $forward_part ]]; then
    result="$result$forward_part"
elif [[ -n $forward_part ]]; then
    # extra slash removal
    result="${forward_part:1}"
fi

echo $result

测试用例 ：

compute_relative.sh "/A/B/C" "/A"           -->  "../.."
compute_relative.sh "/A/B/C" "/A/B"         -->  ".."
compute_relative.sh "/A/B/C" "/A/B/C"       -->  ""
compute_relative.sh "/A/B/C" "/A/B/C/D"     -->  "D"
compute_relative.sh "/A/B/C" "/A/B/C/D/E"   -->  "D/E"
compute_relative.sh "/A/B/C" "/A/B/D"       -->  "../D"
compute_relative.sh "/A/B/C" "/A/B/D/E"     -->  "../D/E"
compute_relative.sh "/A/B/C" "/A/D"         -->  "../../D"
compute_relative.sh "/A/B/C" "/A/D/E"       -->  "../../D/E"
compute_relative.sh "/A/B/C" "/D/E/F"       -->  "../../../D/E/F"

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