m1 mac 上的 `arch -x86_64 zsh` 在內部做什么？

Question

我在嘗試找到安裝舊版本 npm 包的解決方法時遇到了這個命令，這些包在 m1 mac (darwin arm64) 之前出現

我知道這將嘗試啟動具有x86_64架構的 zsh session。 （盡管再次運行arch會給我i386 ，我認為它在某種程度上與x86_64兼容。）

但據我所知，架構在硬件中被定義為處理器芯片。 要模擬不同的架構，您需要一些更重的軟件，例如 virtualbox 或 qemu。

那么arch -x86_64 zsh到底做了什么？ 它真的模擬了不同的架構嗎？

我嘗試閱讀man arch的內容，但對我來說實在是太多了。

...
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

通用二進制文件包含多個單獨的二進制文件。 在執行時，選擇最兼容的二進制文件來實際執行。

arch命令通過顯式選擇要運行的命令來簡單地覆蓋此自動選擇。 能否在當前平台上運行選中的可執行文件是另一回事。

如果你把通用二進制想象成一張 hash 表，那么arch只是查找操作。