问:有没有简单的sh/bash/zsh/fish/…命令打印任何文件的绝对路径我馈送它?
用例:我在目录/a/b中，我想在命令行上打印文件c的完整路径，这样我就可以轻松地将它粘贴到另一个程序:/a/b/c中。这很简单，但是在处理长路径时，一个小程序可能会为我节省5秒左右的时间。因此，让我感到惊讶的是，我找不到一个标准的实用程序来做这件事——真的没有吗?
下面是一个示例实现，abspath.py:
#!/usr/bin/python
# Author: Diggory Hardy <diggory.hardy@gmail.com>
# Licence: public domain
# Purpose: print the absolute path of all input paths
import sys
import os.path
if len(sys.argv)>1:
for i in range(1,len(sys.argv)):
print os.path.abspath( sys.argv[i] )
sys.exit(0)
else:
print >> sys.stderr, "Usage: ",sys.argv[0]," PATH."
sys.exit(1)
在某些情况下，这个问题最上面的答案可能具有误导性。假设你要查找的文件的绝对路径在$ path变量中:
# node is in $PATH variable
type -P node
# /home/user/.asdf/shims/node
cd /tmp
touch node # But because there is a file with the same name inside the current dir check out what happens below
readlink -e node
# /tmp/node
readlink -m node
# /tmp/node
readlink -f node
# /tmp/node
echo "$(cd "$(dirname "node")"; pwd -P)/$(basename "node")"
# /tmp/node
realpath node
# /tmp/node
realpath -e node
# /tmp/node
# Now let's say that for some reason node does not exist in current directory
rm node
readlink -e node
# <nothing printed>
readlink -m node
# /tmp/node # Note: /tmp/node does not exist, but is printed
readlink -f node
# /tmp/node # Note: /tmp/node does not exist, but is printed
echo "$(cd "$(dirname "node")"; pwd -P)/$(basename "node")"
# /tmp/node # Note: /tmp/node does not exist, but is printed
realpath node
# /tmp/node # Note: /tmp/node does not exist, but is printed
realpath -e node
# realpath: node: No such file or directory
基于以上，我可以得出结论:realpath -e和readlink -e可以用于查找文件的绝对路径，我们期望存在于当前目录中，而不受$ path变量的影响。唯一的区别是realpath输出到stderr，但如果没有找到file，两者都会返回错误代码:
cd /tmp
rm node
realpath -e node ; echo $?
# realpath: node: No such file or directory
# 1
readlink -e node ; echo $?
# 1
现在，如果您想要一个存在于$ path中的文件的绝对路径a，那么下面的命令将是合适的，这与当前目录中是否存在同名文件无关。
type -P example.txt
# /path/to/example.txt
# Or if you want to follow links
readlink -e $(type -P example.txt)
# /originalpath/to/example.txt
# If the file you are looking for is an executable (and wrap again through `readlink -e` for following links )
which executablefile
# /opt/bin/executablefile
如果没有，回退到$PATH，示例:
cd /tmp
touch node
echo $(readlink -e node || type -P node)
# /tmp/node
rm node
echo $(readlink -e node || type -P node)
# /home/user/.asdf/shims/node
