Question

查找java二进制文件可能很痛苦：

which java提供/usr/bin/java
lh $(which java)提供/usr/bin/java -> /etc/alternatives/java
lh /etc/alternatives/java提供/etc/alternatives/java -> /usr/lib/jvm/jdk1.8.0_66/bin/java

有没有办法自动关注符号链并打印所有成员？例如whichfollow或follow /usr/bin/java可以提供：

/usr/bin/java
-> /etc/alternatives/java
-> /usr/lib/jvm/jdk1.8.0_66/bin/java

Answer 1

除readlink命令外，GNU / Linux用户还可以使用util-linux包中的namei命令。根据其手册页：

namei使用其参数作为任何类型的Unix文件（符号链接，文件，目录等）的路径名。然后，namei跟随每个路径名，直到找到一个端点（文件，目录，设备节点等）。如果找到符号链接，它会显示该链接，并开始跟随它，缩进输出以显示上下文。

它的输出并不像你想的那样漂亮，但它显示了每条路径组件和节目，如果它是一个目录，符号链接，套接字，块设备，字符设备，FIFO（命名管道）或常规文件。

使用示例：

$ namei  /usr/bin/java

f: /usr/bin/java
 d /
 d usr
 d bin
 l java -> /etc/alternatives/java
   d /
   d etc
   d alternatives
   l java -> /usr/lib/jvm/jre-1.7.0-openjdk/bin/java
     d /
     d usr
     d lib
     d jvm
     l jre-1.7.0-openjdk -> java-1.7.0-openjdk-1.7.0.85/jre
       d java-1.7.0-openjdk-1.7.0.85
       d jre
     d bin
     - java

Answer 2

^{注意：namei（请参阅Anthony Geoghegan's answer）和chase（请参阅Toby Speight's answer）是非常棒的 Linux 选项;这个答案提供：

* 跨平台解决方案

*打印链的每个步骤的绝对路径，即使符号链接是用相对路径定义的。}

考虑 typex utility （由我编写），使用绝对路径打印$PATH中给定实用程序的符号链。在每一步中（typex还提供了额外的信息，类似于type，但比npm install typex -g更广泛。
- 安装了Node.js的最简单安装：--version
- 示例（请注意如何附加使用java获取的版本信息 - 不适用于-version，但使用$ typex awk BINARY: /usr/bin/awk@ -> /etc/alternatives/awk@ -> /usr/bin/gawk [GNU Awk 4.0.1]）：

npm install rreadlink -g

rreadlink 是一个较低级别的实用程序（由我编写），它将符号链接打印为任何给定文件系统路径的绝对路径。
- 安装了Node.js的最简单安装：$ rreadlink -1 "$(which awk)" /usr/bin/awk /etc/alternatives/awk /usr/bin/gawk
- 示例：
```
rreadlinkchain()
```
以下是bash，完全符合POSIX标准的脚本/功能 - 它仅使用POSIX shell language features且仅使用符合POSIX的实用程序调用。它是上面两个实用程序核心的rreadlinkchain "$(which java)"函数的POSIX兼容变体，并且很感激地从this answer改编而来;适用于您的示例：typex

^{兼容性说明：

从npm注册表安装时，rreadlink和bash支持 OS X和Linux ，但可能也会在rreadlinkchain()的BSD系统上运行，手动安装时
如上所述，下面的#!/bin/sh

## -------
# SYNOPSIS
# rreadlinkchain <symLink>
# DESCRIPTION
# Recursive readlink: prints the CHAIN OF SYMLINKS from the input
# file to its ultimate target, as ABSOLUTE paths, with each path on a separate
# line.
# Only the ultimate target's path is canonical, though.
# A broken symlink in the chain causes an error that reports the
# non-existent target.
# An input path that is not a symlink will print its own canonical path.
# LIMITATIONS
# - Won't work with filenames with embedded newlines or filenames containing
# the string ' -> '.
# COMPATIBILITY
# Fully POSIX-compliant.
# EXAMPLES
# # Print the symlink chain of the `git` executable in the $PATH.
# rreadlinkchain "$(which git)"
# # Ditto, using single-line `ls -l`-style format ('a@ -> b')
# rreadlinkchain "$(which git)" | sed -nE -e '$!{a\'$'\n''@ -> ' -e '}; p' | tr -d '\n'
# THANKS
# https://stackoverflow.com/a/1116890/45375
rreadlinkchain() ( # execute in *subshell* to localize the effect of `cd`, ...

target=$1 targetDir= targetName= CDPATH=

# Try to make the execution environment as predictable as possible:
# All commands below are invoked via `command`, so we must make sure that
# `command` itself is not redefined as an alias or shell function.
# (Note that command is too inconsistent across shells, so we don't use it.)
# `command` is a *builtin* in bash, dash, ksh, zsh, and some platforms do not
# even have an external utility version of it (e.g, Ubuntu).
# `command` bypasses aliases and shell functions and also finds builtins
# in bash, dash, and ksh. In zsh, option POSIX_BUILTINS must be turned on for
# that to happen.
{ \unalias command; \unset -f command; } >/dev/null 2>&1
[ -n "$ZSH_VERSION" ] && options[POSIX_BUILTINS]=on # make zsh find *builtins* with `command` too.

while :; do
# Unless the file is a symlink OR exists, we report an error - note that using `-e` with a symlink reports the *target*'s existence, not the symlink's.
[ -L "$target" ] || [ -e "$target" ] || { command printf '%s\n' "ERROR: '$target' does not exist." 1>&2; return 1; }
# !! We use `cd` to change to the target's folder
# !! so we can correctly resolve the full dir. path.
command cd "$(command dirname -- "$target")" # note: cd "" is the same as cd . - i.e., a no-op.
targetDir=$PWD
targetName=$(command basename -- "$target")
[ "$targetName" = '/' ] && targetName='' # !! curiously, `basename /` returns '/'
done=0
if [ ! -L "$targetName" ]; then
# We've found the ultimate target (or the input file wasn't a symlink to begin with).
# For the *ultimate* target we want use `pwd -P` to make sure we use the actual, physical directory,
# (not a symlink) to get the *canonical* path.
targetDir=$(command pwd -P)
done=1
fi
# Print (next) path - note that we manually resolve paths ending
# in /. and /.. to make sure we have a normalized path.
if [ "$targetName" = '.' ]; then
command printf '%s\n' "${targetDir%/}"
elif [ "$targetName" = '..' ]; then
# Caveat: something like /var/.. will resolve to /private (assuming
# /var@ -> /private/var), i.e. the '..' is applied AFTER canonicalization.
command printf '%s\n' "$(command dirname -- "${targetDir}")"
else
command printf '%s\n' "${targetDir%/}/$targetName"
fi
# Exit, if we've hit the non-symlink at the end of the chain.
[ "$done" = 1 ] && break
# File is symlink -> continue to resolve.
# Parse `ls -l` output, which, unfortunately, is the only POSIX-compliant
# way to determine a symlink's target. Hypothetically, this can break with
# filenames containig literal ' -> ' and embedded newlines.
target=$(command ls -l -- "$targetName")
target=${target#* -> }
done
)

rreadlinkchain "$@"
函数完全符合POSIX标准，并且可以在大多数类Unix平台上运行。
功能}

<span>10 000,00</span>
<span class="currency">€</span>

Answer 3

您可以将while与function follow { path="$1" echo "$path" while path=$(readlink "$path"); do echo "-> $path" done } follow "/usr/bin/java"循环一起使用。以下功能可行：

libusb_detach_kernel_driver

Answer 4

考虑安装chase：

示例输出：

$ chase --verbose /usr/bin/java
/usr/bin/java
-> /etc/alternatives/java
-> /usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java
/usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java

包装说明：

套餐：追逐
状态：已安装 自动安装：没有版本：0.5.2-4build2
优先级：可选
部分：universe / utils
维护者：Ubuntu开发人员
架构：amd64
未压缩尺寸：61.4 k
取决于：libc6（＆gt; = 2.3.4），libgc1c2（＆gt; = 1：7.2d）
冲突：追逐
说明：按照符号链接打印出目标文件
Chase是一个小实用程序，用于跟踪a的实际文件符号链接指向 - 追逐符号链接，如果你愿意的话。该成功运行的结果保证是现有文件不是象征性的联系。

如何列出符号链的所有成员？

4 个答案: