Various initial files used by SHELL

The various initial files used by SHELL-Linux general technology-Linux programming and kernel information. The following is a detailed description. The initial files processed during Shell startup can be roughly divided into two types: LoginShell started at LOGIN and second-level SHELL awakened at startup of other files.

The contents of the initial files are all written in ShellScript, which is automatically read at Shell startup (or awakened by other files) and interpreted and implemented by Shell itself, therefore, the first line of the initial file must be [#! /Bin/sh] or [#! /Bin/bash], and do not add implementation attributes.