Linux环境变量配置文件

Linux环境变量配置文件

笔者最近在配置服务器环境,第一次仔细琢磨了一下Linux的几个环境变量配置文件,遂(以Ubuntu22.04为例)写下这一篇博客:

Linux环境变量

在自定义安装软件的时候,经常需要配置环境变量:

  • export命令显示当前系统定义的所有环境变量
  • echo $PATH命令输出当前的PATH环境变量的值

Linux环境变量配置方法一:export PATH

使用export命令直接修改PATH的值,使用该方法立即生效,但只在当前终端有效,切换终端后即失效,配置的环境变量中不要忘了加上原来的配置,即$PATH部分,避免覆盖原来配置。

Linux环境变量配置方法二:修改配置文件

环境变量配置文件有:/etc/profile, /etc/bash.bashrc, /etc/profile.d/*, ~/.bashrc, ~/.profile

  • /etc/profile:为系统的每个用户设置环境信息,当用户第一次登录(login shell)时,该文件被执行
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# /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
fi
fi

if [ -d /etc/profile.d ]; then
for i in /etc/profile.d/*.sh; do
if [ -r $i ]; then
. $i
fi
done
unset i
fi

我们可以观察到Ubuntu22.04的默认/etc/profile会首先执行/etc/bash.bashrc,之后判断是否为root用户,来确定终端提示符是$#,最后逐个执行/etc/profile.d/中的所有脚本
由于 /etc/profile只会在登录时自动执行,因此我们在自动切换用户的时候要注意手动执行source /etc/profile

  • /etc/profile.d:目录中存放的是一些应用程序所需的启动脚本,而这些脚本文件是用来设置一些变量和运行一些初始化过程的。其中包括了颜色、语言、less、vim及which等命令的一些附加设置,其是由/etc/profile调用的,因此也仅在登录时启用。/etc/profile.d/ 比 /etc/profile 好维护。不想要什么变量直接删除/etc/profile.d/下对应的.sh 的shell脚本即可,不用像/etc/profile需要改动此文件。
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(base) ubuntu@VM-4-15-ubuntu:~$ ls /etc/profile.d/
01-locale-fix.sh bash_completion.sh gawk.sh Z97-byobu.sh Z99-cloud-locale-test.sh
apps-bin-path.sh gawk.csh qcloud.sh Z99-cloudinit-warnings.sh
  • /etc/bash.bashrc:为每一个运行bash shell的用户执行此文件,当bash shell被打开时,该文件被读取。
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# 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)
# but only if not SUDOing and have SUDO_PS1 set; then assume smart user.
if ! [ -n "${SUDO_USER}" -a -n "${SUDO_PS1}" ]; then
PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w\$ '
fi

# 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 hint
if [ ! -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
esac
fi

# if the command-not-found package is installed, use it
if [ -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:每个用户都可使用该文件输入专用于自己使用的shell信息,当用户登录时,该文件仅仅执行一次。是交互式login 方式进入 bash 运行的。
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# ~/.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 bash
if [ -n "$BASH_VERSION" ]; then
# include .bashrc if it exists
if [ -f "$HOME/.bashrc" ]; then
. "$HOME/.bashrc"
fi
fi

# set PATH so it includes user's private bin if it exists
if [ -d "$HOME/bin" ] ; then
PATH="$HOME/bin:$PATH"
fi

# set PATH so it includes user's private bin if it exists
if [ -d "$HOME/.local/bin" ] ; then
PATH="$HOME/.local/bin:$PATH"
fi
. "$HOME/.cargo/env"
  • ~/.bashrc:该文件包含专用于你的bash shell的bash信息,当登录时以及每次打开新的shell时,该文件被读取。交互式non-login 方式进入 bash 运行的。
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# ~/.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 bash
if [ -n "$BASH_VERSION" ]; then
# include .bashrc if it exists
if [ -f "$HOME/.bashrc" ]; then
. "$HOME/.bashrc"
fi
fi

# set PATH so it includes user's private bin if it exists
if [ -d "$HOME/bin" ] ; then
PATH="$HOME/bin:$PATH"
fi

# set PATH so it includes user's private bin if it exists
if [ -d "$HOME/.local/bin" ] ; then
PATH="$HOME/.local/bin:$PATH"
fi
. "$HOME/.cargo/env"
(base) ubuntu@VM-4-15-ubuntu:~$ cat ~/.bashrc
# ~/.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 anything
case $- in
*i*) ;;
*) return;;
esac

# don't put duplicate lines or lines starting with space in the history.
# See bash(1) for more options
HISTCONTROL=ignoreboth

# append to the history file, don't overwrite it
shopt -s histappend

# for setting history length see HISTSIZE and HISTFILESIZE in bash(1)
HISTSIZE=1000
HISTFILESIZE=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=yes

if [ -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=
fi
fi

if [ "$color_prompt" = yes ]; then
PS1='${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\$ '
fi
unset color_prompt force_color_prompt

# If this is an xterm set the title to user@host:dir
case "$TERM" in
xterm*|rxvt*)
PS1="\[\e]0;${debian_chroot:+($debian_chroot)}\u@\h: \w\a\]$PS1"
;;
*)
;;
esac

# enable color support of ls and also add handy aliases
if [ -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 aliases
alias ll='ls -alF'
alias la='ls -A'
alias l='ls -CF'

# Add an "alert" alias for long running commands. Use like so:
# sleep 10; alert
alias 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_aliases
fi

# 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
fi
fi
  • ~/.bash_logout:当每次退出系统(退出bash shell)时,执行该文件。
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# ~/.bash_logout: executed by bash(1) when login shell exits.

# when leaving the console clear the screen to increase privacy

if [ "$SHLVL" = 1 ]; then
[ -x /usr/bin/clear_console ] && /usr/bin/clear_console -q
fi

在登录Linux时要执行文件的过程如下:

在刚登录Linux时,首先启动/etc/profile 文件,然后再启动用户目录下的~/.bash_profile~/.bash_login~/.profile文件中的其中一个(根据不同的linux操作系统的不同,命名不一样)

如果~/.bash_profile文件存在的话,一般还会执行 ~/.bashrc文件因为在 ~/.bash_profile文件中一般会有下面的代码:if [ -f ~/.bashrc ] ; then . ./bashrc fi ~/.bashrc。最后,在退出shell时,还会执行~/.bash_logout文件。

执行顺序为:
/etc/profile -> /etc/bash.bashrc -> /etc/profile.d -> ~/.profile -> ~/.bashrc -> ~/.bash_logout

笔者在写的时候也注意到貌似和网上一些介绍不太一样,但是这是笔者所观察到的情况,也没有去查阅Linux官方文档,因此可以辩证地看待。