关于Linux下的环境变量

来源：互联网发布：linux 安装jira7 编辑：程序博客网时间：2024/06/05 22:50

一、交互式shell和非交互式shell

要搞清bashrc与profile的区别，首先要弄明白什么是交互式shell和非交互式shell，什么是login shell 和non-login shell。

【交互模式】

交互式模式就是shell等待你的输入，并且执行你提交的命令。这种模式被称作交互式是因为shell与用户进行交互。这种模式也是大多数用户非常熟悉的：登录、执行一些命令、签退。当你签退后，shell也终止了。

【非交互模式】

shell也可以运行在另外一种模式：非交互式模式。在这种模式下，shell不与你进行交互，而是读取存放在文件中的命令,并且执行它们。当它读到文件的结尾，shell也就终止了。

bashrc与profile都用于保存用户的环境信息，bashrc用于交互式non-loginshell，而profile用于交互式login shell。

二、几种环境变量配置文件

/etc/profile和/etc/bashrc都是对所有用户生效！

~/.bash_profile和~/.bashrc只对当前用户生效。~表示当前用户的家目录。

/etc/profile中设置的变量（全局）可以作用于任何用户，而~/.bashrc中设置的变量（局部）只能继承/etc/profile中的变量，它们是父子关系。

~/.bash_profile是交互式、login方式进入bash运行的；

~/.bashrc是交互式、non-login方式进入bash运行的；

1. /etc/profile

该文件为系统的每个用户设置环境信息，当用户第一次登录时，该文件被执行。并从/etc/profile.d目录的配置文件中搜集shell的设置。

[root@CentOS6 ~]# more /etc/profile# /etc/profile# System wide environment and startup programs, for login setup# Functions and aliases go in /etc/bashrc# It's NOT a good idea to change this file unless you know what you# are doing. It's much better to create a custom.sh shell script in# /etc/profile.d/ to make custom changes to your environment, as this# will prevent the need for merging in future updates.pathmunge () {    case ":${PATH}:" in        *:"$1":*)            ;;        *)            if [ "$2" = "after" ] ; then                PATH=$PATH:$1            else                PATH=$1:$PATH            fi    esac}if [ -x /usr/bin/id ]; then    if [ -z "$EUID" ]; then        # ksh workaround        EUID=`id -u`        UID=`id -ru`    fi    USER="`id -un`"    LOGNAME=$USER    MAIL="/var/spool/mail/$USER"fi# Path manipulationif [ "$EUID" = "0" ]; then    pathmunge /sbin    pathmunge /usr/sbin    pathmunge /usr/local/sbinelse    pathmunge /usr/local/sbin after    pathmunge /usr/sbin after    pathmunge /sbin afterfiHOSTNAME=`/bin/hostname 2>/dev/null`HISTSIZE=1000if [ "$HISTCONTROL" = "ignorespace" ] ; then    export HISTCONTROL=ignorebothelse    export HISTCONTROL=ignoredupsfiexport PATH USER LOGNAME MAIL HOSTNAME HISTSIZE HISTCONTROL# By default, we want umask to get set. This sets it for login shell# Current threshold for system reserved uid/gids is 200# You could check uidgid reservation validity in# /usr/share/doc/setup-*/uidgid fileif [ $UID -gt 199 ] && [ "`id -gn`" = "`id -un`" ]; then    umask 002else    umask 022fifor i in /etc/profile.d/*.sh ; do    if [ -r "$i" ]; then        if [ "${-#*i}" != "$-" ]; then            . "$i"        else            . "$i" >/dev/null 2>&1        fi    fidoneunset iunset -f pathmunge

2. /etc/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。

# /etc/bashrc# System wide functions and aliases# Environment stuff goes in /etc/profile# It's NOT a good idea to change this file unless you know what you# are doing. It's much better to create a custom.sh shell script in# /etc/profile.d/ to make custom changes to your environment, as this# will prevent the need for merging in future updates.# are we an interactive shell?if [ "$PS1" ]; then  if [ -z "$PROMPT_COMMAND" ]; then    case $TERM in    xterm*)        if [ -e /etc/sysconfig/bash-prompt-xterm ]; then            PROMPT_COMMAND=/etc/sysconfig/bash-prompt-xterm        else            PROMPT_COMMAND='printf "\033]0;%s@%s:%s\007" "${USER}" "${HOSTNAME%%.*}" "${PWD/#$HOME/~}"'        fi        ;;    screen)        if [ -e /etc/sysconfig/bash-prompt-screen ]; then            PROMPT_COMMAND=/etc/sysconfig/bash-prompt-screen        else            PROMPT_COMMAND='printf "\033]0;%s@%s:%s\033\\" "${USER}" "${HOSTNAME%%.*}" "${PWD/#$HOME/~}"'        fi        ;;    *)        [ -e /etc/sysconfig/bash-prompt-default ] && PROMPT_COMMAND=/etc/sysconfig/bash-prompt-default        ;;      esac  fi  # Turn on checkwinsize  shopt -s checkwinsize  [ "$PS1" = "\\s-\\v\\\$ " ] && PS1="[\u@\h \W]\\$ "  # You might want to have e.g. tty in prompt (e.g. more virtual machines)  # and console windows  # If you want to do so, just add e.g.  # if [ "$PS1" ]; then  #   PS1="[\u@\h:\l \W]\\$ "  # fi  # to your custom modification shell script in /etc/profile.d/ directoryfiif ! shopt -q login_shell ; then # We're not a login shell    # Need to redefine pathmunge, it get's undefined at the end of /etc/profile    pathmunge () {        case ":${PATH}:" in            *:"$1":*)                ;;            *)                if [ "$2" = "after" ] ; then                    PATH=$PATH:$1                else                    PATH=$1:$PATH                fi        esac    }    # By default, we want umask to get set. This sets it for non-login shell.    # Current threshold for system reserved uid/gids is 200    # You could check uidgid reservation validity in    # /usr/share/doc/setup-*/uidgid file    if [ $UID -gt 199 ] && [ "`id -gn`" = "`id -un`" ]; then       umask 002    else       umask 022    fi    # Only display echos from profile.d scripts if we are no login shell    # and interactive - otherwise just process them to set envvars    for i in /etc/profile.d/*.sh; do        if [ -r "$i" ]; then            if [ "$PS1" ]; then                . "$i"            else                . "$i" >/dev/null 2>&1            fi        fi    done    unset i    unset pathmungefi# vim:ts=4:sw=4

3. ~/.bash_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。默认情况下，他设置一些环境变量，执行用户的

~/.bashrc文件。

[root@CentOS6 ~]# more ~/.bash_profile# .bash_profile# Get the aliases and functionsif [ -f ~/.bashrc ]; then        . ~/.bashrcfi# User specific environment and startup programsPATH=$PATH:$HOME/bin:/usr/local/mysql/binexport PATH

4.~/.bashrc

该文件包含专用于你的bash shell的bash信息。当登录时及每次打开新的shell时，该文件被读取。

每个用户都有一个~/.bashrc文件，在用户目录下。

[root@CentOS6 ~]# more ~/.bashrc# .bashrc# User specific aliases and functionsalias rm='rm -i'alias cp='cp -i'alias mv='mv -i'# Source global definitionsif [ -f /etc/bashrc ]; then        . /etc/bashrcfi

5. ~/.bash_logout

当每次退出系统时（退出bash shell），执行该文件。

[root@CentOS6 ~]# more ~/.bash_logout# ~/.bash_logout

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