Flag passed to the shell to execute "!" and ":!" commands; e.g., "bash.exe -c ls", "powershell.exe -Command dir", or "cmd.exe /c dir". For MS-Windows, the default is set according to the value of 'shell', to reduce the need to set this option by the user. On Unix it can have more than one flag. Each white space separated part is passed as an argument to the shell command. See option-backslash about including spaces and backslashes. Also see dos-shell and dos-powershell for MS-Windows. This option cannot be set from a modeline or in the sandbox, for security reasons.

(default: "-c"; Win32, when 'shell' contains "powershell": "-Command", or when it does not contain "sh" somewhere: "/c")