m1 mac 上的 `arch -x86_64 zsh` 在内部做什么？

Question

我在尝试找到安装旧版本 npm 包的解决方法时遇到了这个命令，这些包在 m1 mac (darwin arm64) 之前出现

我知道这将尝试启动具有x86_64架构的 zsh session。 （尽管再次运行arch会给我i386 ，我认为它在某种程度上与x86_64兼容。）

但据我所知，架构在硬件中被定义为处理器芯片。 要模拟不同的架构，您需要一些更重的软件，例如 virtualbox 或 qemu。

那么arch -x86_64 zsh到底做了什么？ 它真的模拟了不同的架构吗？

我尝试阅读man arch的内容，但对我来说实在是太多了。

...
DESCRIPTION
     The arch command with no arguments, displays the machine's architecture type.

     The other use of the arch command is to run a selected architecture of a universal binary.  A universal
     binary contains code that can run on different architectures.  By default, the operating system will select
     the architecture that most closely matches the processor type.  A 64-bit architecture is preferred over a
     32-bit architecture on a 64-bit processor, while only 32-bit architectures can run on a 32-bit processor.

     When the most natural architecture is unavailable, the operating system will try to pick another
     architecture.  On 64-bit processors, a 32-bit architecture is tried.  Otherwise, no architecture is run, and
     an error results.

     The arch command can be used to alter the operating system's normal selection order.  The most common use is
     to select the 32-bit architecture on a 64-bit processor, even if a 64-bit architecture is available.

     The arch_name argument must be one of the currently supported architectures:

           i386     32-bit intel

           x86_64   64-bit intel

           x86_64h  64-bit intel (haswell)

           arm64    64-bit arm

           arm64e   64-bit arm (Apple Silicon)
...

Answer 1

通用二进制文件包含多个单独的二进制文件。 在执行时，选择最兼容的二进制文件来实际执行。

arch命令通过显式选择要运行的命令来简单地覆盖此自动选择。 能否在当前平台上运行选中的可执行文件是另一回事。

如果你把通用二进制想象成一张 hash 表，那么arch只是查找操作。