为什么我能够直接从bash中执行的JAR？ [英] Why am I able to execute JARs directly from bash?

问题描述

我是一个长期的Java的家伙，知道路与中引用一个主类运行一个JAR一个 MANIFEST.MF 的Jar文件中很容易：

I'm a longtime Java guy, and know that the way to run a JAR with a main class referenced in a MANIFEST.MF file within the Jar is easy:

Java的罐子theJar.jar

我是用这个来启动服务器Fabric3（包含在其标准发行斌/的server.jar ）。我注意到，当我从分发压缩包解压缩它，它被标记为可执行文件。一时兴起，我试过

I was using this to start up the Fabric3 server (contained in bin/server.jar in its standard distribution). I noticed that when I unpacked it from the distribution tarball, it was flagged as executable. On a whim, I tried

./的server.jar

从我庆典命令行（庆典 4.1.5版本在Ubuntu 10.10），你瞧，服务器启动，如果我输入了正常 Java的罐子... 命令。该JAR的结构像一个正常的JAR;我做了一个头就可以了，也没有＃！中的前几个字节命令，这样庆典不应神奇知道启动Java虚拟机吧，对不对？或者有这个版本的庆典的成长与正确适当的清单开始的JAR文件的能力吗？好奇之心想知道...

from my bash command line (bash version 4.1.5 in Ubuntu 10.10), and lo and behold, the server started up as if I had typed the normal java -jar ... command. The JAR is structured like a normal JAR; I did a head on it, and there was no #! command in the first few bytes, so bash shouldn't magically know to start a Java VM with it, right? Or has this version of bash grown the ability to start JARs with a proper manifest correctly? Inquiring minds want to know...

推荐答案

这可能不是bash中的一项功能都没有。如果您运行的是Linux（如你已标记），你可能有 binfmt_misc 内核模块，这确实是一个神奇的一点，当你尝试执行程序。基本上，这样做是它扩展了二进制格式的Linux可以从仅仅精灵执行也包括一些用户定义的格式，有足够的指令来运行它们。

This may not be a feature of bash at all. If you are running linux (as you have tagged) you may have the binfmt_misc kernel module, which does a little bit of magic, when you try to execute a program. Basically what this does is it extends the binary formats that linux can execute from just elf to also include some user defined formats, with enough instructions to run them.

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