bash 如何在shell的if条件中找到选项
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How to find the options in if conditions of shell
提问by John
In one of my shell script, I'm seeing
在我的一个 shell 脚本中，我看到
if [[ ! -d directory1 || ! -L directory ]] ; then
What does -dand -Loption mean here? Where can I find information about the options to use in an ifcondition?
是什么-d和-L选项的意思吗？在哪里可以找到有关在条件中使用的选项的信息if？
回答by Paused until further notice.
You can do help testwhich will show most of the options accepted by the [[command.
您可以这样做help test，这将显示[[命令接受的大多数选项。
You can also do help [which will show additional information. You can do help [[to get information on that type of conditional.
您也可以这样做help [，这将显示附加信息。您可以这样做help [[以获取有关该类型条件的信息。
Also see man bashin the "CONDITIONAL EXPRESSIONS" section.
另请参见man bash“条件表达式”部分。
回答by Levon
The -dchecks whether the given directory exists. The -Ltest for a symbolic link.
该-d检查是否给定的目录是否存在。-L符号链接的 测试。
The File test operatorsfrom the Advanced Bash-Scripting Guideexplain the various options. And here is the man page for bashwhich can also be found by typing man bashin the terminal.
该文件的测试运营商从高级Bash脚本编程指南解释了各种选项。这是bash的手册页，也可以通过man bash在终端中键入来找到。
回答by camh
bashhas built-in help with the helpcommand. You can easily find out the options to a bash built-in using help:
bash具有help命令的内置帮助。您可以使用以下命令轻松找到内置 bash 的选项help：
$ help [[
...
Expressions are composed of the same primaries used by the `test' builtin
...
$ help test
test: test [expr]
Evaluate conditional expression.
...
[the answer you want]
回答by David W.
In Bourne shell, [and testwere linked to the same executable. Thus, you can find a lot of the various testsavailable in the testmanpage.
在Bourne shell中，[并test分别连接到同一个可执行文件。因此，您可以在测试联机帮助页中找到许多可用的各种测试。
This:
这个：
if [[ ! -d directory1 || ! -L directory ]] ; then
is saying if directory1is not a directory orif directoryis not a link.
是说，如果directory1不是目录或者如果directory不是链接。
I believe the correct syntax should be:
我相信正确的语法应该是：
if [[ ! -d $directory1 ] || [ ! -L $directory ]] ; then
or
或者
if [[ ! -d $directory1 -o ! -L $directory ]] ; then
Is the line in your OP correct?
您的 OP 中的行是否正确？
