bash “if -e”和“if -f”之间的区别
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Difference between 'if -e' and 'if -f'
提问by Ahatius
There are two switches for the ifcondition which check for a file: -eand -f.
if检查文件的条件有两个开关：-e和-f。
What is the difference between those two?
这两者有什么区别？
回答by Emil Vatai
See: http://tldp.org/LDP/Bash-Beginners-Guide/html/sect_07_01.html
请参阅：http: //tldp.org/LDP/Bash-Beginners-Guide/html/sect_07_01.html
I believe those aren't "if switches", rather "test switches" (because you have to use them inside [] brackets.
我相信那些不是“if 开关”，而是“测试开关”（因为你必须在 [] 括号内使用它们。
But the difference is:
但不同的是：
[ -e FILE ]True if FILE exists.
[ -e FILE ]如果 FILE 存在，则为真。
This will return truefor both /etc/hostsand /dev/nulland for directories.
这将返回真正的两个/etc/hosts和/dev/null和目录。
[ -f FILE ]True if FILE exists and is a regular file.
This will return truefor /etc/hostsand falsefor /dev/null(because it is not a regular file), and falsefor /devsince it is a directory.
[ -f FILE ]如果 FILE 存在并且是常规文件，则为真。这将返回truefor/etc/hosts和falsefor /dev/null（因为它不是常规文件），以及falsefor/dev因为它是一个目录。
回答by jman
$ man bash
-e file
True if file exists.
-f file
True if file exists and is a regular file.
A regular file is something that isn't a directory, symlink, socket, device, etc.
常规文件不是目录、符号链接、套接字、设备等。
回答by Ignacio Vazquez-Abrams
-echecks for anytype of filesystem object; -fonlychecks for a regular file.
-e检查任何类型的文件系统对象；-f只检查常规文件。
回答by gitaarik
The if statement actually uses the program 'test' for the tests. You could write if statements two ways:
if 语句实际上使用程序“test”进行测试。您可以通过两种方式编写 if 语句：
if [ -e filename ];
or
或者
if test -e filename;
If you know this, you can easily check the man page for 'test' to find out the meanings of the different tests:
如果您知道这一点，您可以轻松查看“test”的手册页以找出不同测试的含义：
man test
