如何在bash中找到指向符号链接的符号链接

Question

我正在准备一个 bash 脚本来验证符号链接的正确性。我想诊断什么时候：

1. @symlink 已损坏
2. @symlink 指向另一个@symlink --（用符号链接链的最终目标修复它）
3. @symlink 指向另一个已损坏的@symlink
4. @symlinks 链是一个循环

在诊断符号链接指向符号链接时，我对第 2 点有很大的问题。

我尝试使用 readlink，但它返回符号链接链的最终目标，而不是指向符号链接名称。我试图在没有-f 参数的情况下运行它，但没有帮助。然后与 find 的组合给了我糟糕的结果...
谁能帮我解决这个问题？

下面我将我的代码粘贴到当前版本中。

failed=0

for file in path/*
do
    if [[ -L "$file" ]]
    then
        if [[ ! -a "$file" ]]
        then
            echo "Symlink '$file' is broken -- target object doesn't exists."
            failed=1
        elif [[ -L "$(readlink -f $file)" ]]
        then
            echo "Symlink '$file' points to another symlink: '$(readlink $file)'"
            failed=1
        fi
    fi
done
exit $failed

更新

测试文件结构（其中 symlinks.sh 是讨论 bash 脚本）：

Answer 1

从您的问题描述中不清楚应如何处理传递链末端的断开链接。我会简单地报告一个错误并继续前进。

#!/bin/sh
rc=0
for file in path/*; do
    if [ -L "$file" ]; then
        nfile=$file
        while [ -L "$nfile" ]; do
            nfile=$(cd $(dirname "$nfile"); abspath $(readlink "$nfile"))
        done
        if ! [ -r "$nfile" ]; then
            echo "$0: $file eventually resolves to nonexistent target $nfile" >&2
            rc=1
        else
            # FIXME: maybe avoid doing this needlessly?
            rm "$file"
            ln -s "$nfile" "$file"
        fi
    fi
done
exit "$rc"

我是否正确理解您希望将符号链接（等递归）的符号链接替换为最终目标的符号链接？这个脚本可以做到这一点，尽管它会重写所有解析的符号链接。对此进行优化以避免不必要的操作留作练习。

Answer 2

我不是 bash 方面的专家，因此可能有人向我们展示了更简单的解决方案，但这次我分享了我的脚本（它确保了具有相对链接的符号链接的相对路径）：

#!/bin/sh
# The task is to create bash script, which validates symlinks and reports when:
# (1) - symlink is broken
# (2) - symlink target point is broken
# (3) - symlink points to another symlink
# (4) - symlinks chain is a cycle

FAILED=0
FIX_SYMLINKS=false
DIR_UP="../"


function file_under_symlink_absolute_path {
    local file_under_symlink="$(readlink $1)"
    local file_dirname="$(dirname $1)"

    if [[ "$file_under_symlink" == *"$DIR_UP"* ]]; then
        if [[ "$file_under_symlink" == *"$DIR_UP$DIR_UP"* ]]; then
            while [[ "$file_under_symlink" == *"$DIR_UP"* ]]; do
                local file_under_symlink="${file_under_symlink#$DIR_UP}"

                if [[ "$file_dirname" == *"/"* ]]; then
                    local file_dirname="${file_dirname%/*}"
                else
                    local file_dirname=""
                fi
            done

            if [[ "$file_dirname" != "" ]]; then
                local file_dirname="$file_dirname/$file_under_symlink"
            else
                local file_dirname="$file_under_symlink"
            fi
        else
            if [[ "$file_dirname" == *"/"* ]]; then
                local file_dirname="${file_dirname%/*}/${file_under_symlink#$DIR_UP}"
            else
                local file_dirname="${file_under_symlink#$DIR_UP}"
            fi
        fi
    else
        local file_dirname="$file_dirname/$file_under_symlink"
    fi

    echo "$(pwd)/$file_dirname"
}

function file_under_symlink_relative_path {
    local file_dirname="$(dirname $1)"
    local symlink_target="$2"
    local file_under_symlink="$3"

    if [[ "$symlink_target" == *"$file_dirname"* ]]; then
        local prefix2cut="$(pwd)/$file_dirname"
        local target="${symlink_target##$prefix2cut}"

    else
        local symlink_target_dirname="$(dirname $symlink_target)"
        local symlink_target_basename="$(basename $symlink_target)"

        if [[ "$file_under_symlink" == "$symlink_target_dirname"* ]]; then
            local level_diff="${file_under_symlink#$symlink_target_dirname/}"
            local target="$symlink_target_basename"

            while [[ "$level_diff" == *"/"* ]]; do
                local level_diff="${level_diff%/*}"
                local target="$DIR_UP$target"
            done
        else
            if [[ "$file_dirname" == *"/"* ]]; then
                local prefix2cut="$(pwd)/${file_dirname%/*}/"
            else
                local prefix2cut="$(pwd)/"
            fi
            local target="$DIR_UP${symlink_target#$prefix2cut}"
        fi
    fi

    echo "$target"
}

function valid_symlinks {
    local current_dir="$1"

    for file in "$current_dir"/*; do
        if [[ -d "$file" ]]; then
            valid_symlinks "$file"

        elif [[ -L "$file" ]]; then
            local symlink_target=$(readlink -e "$file")
            local file_under_symlink_abs="$(file_under_symlink_absolute_path $file)"

            # reports (1), (2), (4)
            if [[ ! -a "$file" ]]; then
                echo "BROKEN   Symlink '$file' is broken, target object doesn't exists."
                FAILED=1

            # reports (3)
            # it happends when file under symlink is not the symlink target file
            elif [[ "$file_under_symlink_abs" != "$symlink_target" ]]; then
                if $FIX_SYMLINKS && [[ -r "$symlink_target" ]]; then
                    local target="$(file_under_symlink_relative_path $file $symlink_target $file_under_symlink_abs)"

                    echo "Symlink '$file' points to another symlink. It will be replace with direct symlink to target '$target'."
                    ln -fs "$target" "$file"
                else
                    local target="${file_under_symlink_abs#$(pwd)/}"

                    echo "Symlink '$file' points to another symlink '$target'."
                    FAILED=1
                fi
            fi
        fi
    done
}

if [[ -d "$1" ]]; then
    start_point=${1#$(pwd)/}
    start_point=${start_point%/}

    valid_symlinks "$start_point"
else
    echo "ERROR: You have to specify the start location path."
    FAILED=1
fi

exit $FAILED