Ubuntu /etc目录下profile、bash.bashrc文件和用户目录下.profile、.bashrc文件的作用和区别

相关概念：
Login Shell：需要输入账号密码Shell，比如tty1-tty6终端、通过ssh登录的终端
Non-login Shell：不需要输入账号密码的Shell，比如图形模式下Ctrl+Alt+T得到的Terminal、Shell下的子进程

区别：
/etc/profile、/etc/bash.bashrc文件是针对所有用户来说的，每个用户登录时都会执行，其中/etc/profile只执行一次，而/etc/bash.bashrc在每次Shell时都会执行。
~/.profile、~/.bashrc文件是针对单个用户来说的，每个用户目录下都会有这两个文件，其中~/.profile在Login Shell登录时执行，~/.bashrc在Non-login Shell登录时执行。

相关：
/etc/environment文件，这个文件只有一行内容：

PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games"

也就是将以下目录来初始化PATH

/sbin
/bin
/usr/sbin
/usr/bin
/usr/local/sbin
/usr/local/bin
/usr/games
/usr/local/games

以下是这四个文件的源代码，供大家方便阅读：

/etc/profile文件：

# /etc/profile: system-wide .profile file for the Bourne shell (sh(1))# and Bourne compatible shells (bash(1), ksh(1), ash(1), ...).if [ "$PS1" ]; then  if [ "$BASH" ] && [ "$BASH" != "/bin/sh" ]; then    # The file bash.bashrc already sets the default PS1.    # PS1='\h:\w\$ '    if [ -f /etc/bash.bashrc ]; then      . /etc/bash.bashrc    fi  else    if [ "`id -u`" -eq 0 ]; then      PS1='# '    else      PS1='$ '    fi  fifiif [ -d /etc/profile.d ]; then  for i in /etc/profile.d/*.sh; do    if [ -r $i ]; then      . $i    fi  done  unset ifi

/etc/bash.bashrc文件：

# System-wide .bashrc file for interactive bash(1) shells.# To enable the settings / commands in this file for login shells as well,# this file has to be sourced in /etc/profile.# If not running interactively, don't do anything[ -z "$PS1" ] && return# check the window size after each command and, if necessary,# update the values of LINES and COLUMNS.shopt -s checkwinsize# set variable identifying the chroot you work in (used in the prompt below)if [ -z "${debian_chroot:-}" ] && [ -r /etc/debian_chroot ]; then    debian_chroot=$(cat /etc/debian_chroot)fi# set a fancy prompt (non-color, overwrite the one in /etc/profile)PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w\$ '# Commented out, don't overwrite xterm -T "title" -n "icontitle" by default.# If this is an xterm set the title to user@host:dir#case "$TERM" in#xterm*|rxvt*)#    PROMPT_COMMAND='echo -ne "\033]0;${USER}@${HOSTNAME}: ${PWD}\007"'#    ;;#*)#    ;;#esac# enable bash completion in interactive shells#if ! shopt -oq posix; then#  if [ -f /usr/share/bash-completion/bash_completion ]; then#    . /usr/share/bash-completion/bash_completion#  elif [ -f /etc/bash_completion ]; then#    . /etc/bash_completion#  fi#fi# sudo hintif [ ! -e "$HOME/.sudo_as_admin_successful" ] && [ ! -e "$HOME/.hushlogin" ] ; then    case " $(groups) " in *\ admin\ *|*\ sudo\ *)    if [ -x /usr/bin/sudo ]; then        cat <<-EOF        To run a command as administrator (user "root"), use "sudo <command>".        See "man sudo_root" for details.        EOF    fi    esacfi# if the command-not-found package is installed, use itif [ -x /usr/lib/command-not-found -o -x /usr/share/command-not-found/command-not-found ]; then        function command_not_found_handle {                # check because c-n-f could've been removed in the meantime                if [ -x /usr/lib/command-not-found ]; then                   /usr/lib/command-not-found -- "$1"                   return $?                elif [ -x /usr/share/command-not-found/command-not-found ]; then                   /usr/share/command-not-found/command-not-found -- "$1"                   return $?                else                   printf "%s: command not found\n" "$1" >&2                   return 127                fi        }fi

~/.profile文件

# ~/.profile: executed by the command interpreter for login shells.# This file is not read by bash(1), if ~/.bash_profile or ~/.bash_login# exists.# see /usr/share/doc/bash/examples/startup-files for examples.# the files are located in the bash-doc package.# the default umask is set in /etc/profile; for setting the umask# for ssh logins, install and configure the libpam-umask package.#umask 022# if running bashif [ -n "$BASH_VERSION" ]; then    # include .bashrc if it exists    if [ -f "$HOME/.bashrc" ]; then        . "$HOME/.bashrc"    fifi# set PATH so it includes user's private bin directoriesPATH="$HOME/bin:$HOME/.local/bin:$PATH"

~/.bashrc文件

# ~/.bashrc: executed by bash(1) for non-login shells.# see /usr/share/doc/bash/examples/startup-files (in the package bash-doc)# for examples# If not running interactively, don't do anythingcase $- in    *i*) ;;      *) return;;esac# don't put duplicate lines or lines starting with space in the history.# See bash(1) for more optionsHISTCONTROL=ignoreboth# append to the history file, don't overwrite itshopt -s histappend# for setting history length see HISTSIZE and HISTFILESIZE in bash(1)HISTSIZE=1000HISTFILESIZE=2000# check the window size after each command and, if necessary,# update the values of LINES and COLUMNS.shopt -s checkwinsize# If set, the pattern "**" used in a pathname expansion context will# match all files and zero or more directories and subdirectories.#shopt -s globstar# make less more friendly for non-text input files, see lesspipe(1)[ -x /usr/bin/lesspipe ] && eval "$(SHELL=/bin/sh lesspipe)"# set variable identifying the chroot you work in (used in the prompt below)if [ -z "${debian_chroot:-}" ] && [ -r /etc/debian_chroot ]; then    debian_chroot=$(cat /etc/debian_chroot)fi# set a fancy prompt (non-color, unless we know we "want" color)case "$TERM" in    xterm-color|*-256color) color_prompt=yes;;esac# uncomment for a colored prompt, if the terminal has the capability; turned# off by default to not distract the user: the focus in a terminal window# should be on the output of commands, not on the prompt#force_color_prompt=yesif [ -n "$force_color_prompt" ]; then    if [ -x /usr/bin/tput ] && tput setaf 1 >&/dev/null; then        # We have color support; assume it's compliant with Ecma-48        # (ISO/IEC-6429). (Lack of such support is extremely rare, and such        # a case would tend to support setf rather than setaf.)        color_prompt=yes    else        color_prompt=    fifiif [ "$color_prompt" = yes ]; then    PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ 'else    PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w\$ 'fiunset color_prompt force_color_prompt# If this is an xterm set the title to user@host:dircase "$TERM" inxterm*|rxvt*)    PS1="\[\e]0;${debian_chroot:+($debian_chroot)}\u@\h: \w\a\]$PS1"    ;;*)    ;;esac# enable color support of ls and also add handy aliasesif [ -x /usr/bin/dircolors ]; then    test -r ~/.dircolors && eval "$(dircolors -b ~/.dircolors)" || eval "$(dircolors -b)"    alias ls='ls --color=auto'    #alias dir='dir --color=auto'    #alias vdir='vdir --color=auto'    alias grep='grep --color=auto'    alias fgrep='fgrep --color=auto'    alias egrep='egrep --color=auto'fi# colored GCC warnings and errors#export GCC_COLORS='error=01;31:warning=01;35:note=01;36:caret=01;32:locus=01:quote=01'# some more ls aliasesalias ll='ls -alF'alias la='ls -A'alias l='ls -CF'# Add an "alert" alias for long running commands.  Use like so:#   sleep 10; alertalias alert='notify-send --urgency=low -i "$([ $? = 0 ] && echo terminal || echo error)" "$(history|tail -n1|sed -e '\''s/^\s*[0-9]\+\s*//;s/[;&|]\s*alert$//'\'')"'# Alias definitions.# You may want to put all your additions into a separate file like# ~/.bash_aliases, instead of adding them here directly.# See /usr/share/doc/bash-doc/examples in the bash-doc package.if [ -f ~/.bash_aliases ]; then    . ~/.bash_aliasesfi# enable programmable completion features (you don't need to enable# this, if it's already enabled in /etc/bash.bashrc and /etc/profile# sources /etc/bash.bashrc).if ! shopt -oq posix; then  if [ -f /usr/share/bash-completion/bash_completion ]; then    . /usr/share/bash-completion/bash_completion  elif [ -f /etc/bash_completion ]; then    . /etc/bash_completion  fifi