“#！/usr/bin/env bash"和“#！/usr/bin/env bash"之间有什么区别?和“#！/usr/bin/bash"? [英] What is the difference between "#!/usr/bin/env bash" and "#!/usr/bin/bash"?
问题描述
在Bash脚本的标题中，这两个语句之间有什么区别:
In the header of a Bash script, what's the difference between those two statements:
-
#!/usr/bin/env bash
#!/usr/bin/bash
当我查阅env 手册页时，得到以下定义:
When I consulted the env man page, I get this definition:
env - run a program in a modified environment
这是什么意思?
推荐答案
通过/usr/bin/env运行命令的好处是可以查找当前 en 程序中程序的默认版本
Running a command through /usr/bin/env has the benefit of looking for whatever the default version of the program is in your current environment.
这样，您不必在系统上的特定位置查找它，因为这些路径可能在不同系统上的不同位置.只要它在您的路径中，它就会找到它.
This way, you don't have to look for it in a specific place on the system, as those paths may be in different locations on different systems. As long as it's in your path, it will find it.
一个缺点是，如果您希望支持Linux，则您将无法传递多个参数(例如，您将无法编写/usr/bin/env awk -f)，例如
One downside is that you will be unable to pass more than one argument (e.g. you will be unable to write /usr/bin/env awk -f) if you wish to support Linux, as POSIX is vague on how the line is to be interpreted, and Linux interprets everything after the first space to denote a single argument. You can use /usr/bin/env -S on some versions of env to get around this, but then the script will become even less portable and break on fairly recent systems (e.g. even Ubuntu 16.04 if not later).
另一个缺点是，由于您没有调用显式可执行文件，因此很可能会出错，并且在多用户系统上存在安全问题(例如，如果有人设法在路径中获取名为bash的可执行文件).
Another downside is that since you aren't calling an explicit executable, it's got the potential for mistakes, and on multiuser systems security problems (if someone managed to get their executable called bash in your path, for example).
#!/usr/bin/env bash #lends you some flexibility on different systems
#!/usr/bin/bash #gives you explicit control on a given system of what executable is called
在某些情况下，首选第一个(例如，运行带有多个python版本的python脚本，而不必重新编写可执行代码行).但是在以安全性为重点的情况下，后者是首选，因为它限制了代码注入的可能性.
In some situations, the first may be preferred (like running python scripts with multiple versions of python, without having to rework the executable line). But in situations where security is the focus, the latter would be preferred, as it limits code injection possibilities.
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