为什么'script'实用程序需要在Cygwin下使用SHELL（并且在Linux下正常工作）？

Question

看看我的会议：

  gavenko+bash# echo $SHELL
  /bin/bash
  gavenko+bash# script
  Script started, file - typescript
                                   sh-4.1$ ^C
  sh-4.1$ exit
  Script started, file - typescript


  gavenko+bash# SHELL=/bin/bash script
  Script started, file - typescript
                                   gavenko+bash# ^C
  gavenko+bash# exit
  Script started, file - typescript


  gavenko+bash# export SHELL
  gavenko+bash# script
  Script started, file - typescript
                                   gavenko+bash# ^C
  gavenko+bash# exit

正如您所看到的，第一次脚本不使用SHELL，第二次使用它 第三次使用它。

所以SHELL env var不会被bash导出......

为什么？

这是正确的添加

  export SHELL

到'〜/ .bashrc'？

Answer 1

请参阅我的问题的答案：http://cygwin.com/ml/cygwin/2011-10/msg00269.html

This is a bug in bash which hides broken behavior
in the OS.

Bash expects this to be an existing environment variable,
and it usually is in normal Unix like operating systems.

However, bash internally sets the variable if it is
missing (without exporting it):

`SHELL'
The full pathname to the shell is kept in this environment
variable. If it is not set when the shell starts, Bash assigns to
it the full pathname of the current user's login shell.

It is correct not to export the variable. Bash might not be
the user's shell, so it has no right to introduce itself as
the SHELL to child processes.