Linux学习---shell编程（04-环境变量配置文件）

1.source命令

source 配置文件 或者 . 配置文件
# 让配置文件立即生效。

 

2. 环境变量配置文件作用

环境变量配置文件中主要定义对系统的操作环境生效的默认环境变量，比如PATH, PS1, HOSTNAME等。

PATH = “$PATH”:/Users/yesiming#临时生效

3.环境变量的位置

/etc/profile

/etc/profile.d/*.sh

~/.bash_profile

~/.bashrc

/etc/bashrc

 

执行顺序

/etc/profile à/etc/profile.d/*.sh(lang.sh)

à~/.bash_profileà~/.bashrc à/etc/bashrc(这里有了不登录设置环境变量)

 

/etc/profile的作用

pathmunge () { #设置path     case":${PATH}:"in         *:"$1":*)             ;;         *)             if ["$2"="after"] ; then                 PATH=$PATH:$1             else                 PATH=$1:$PATH             fi     esac }     if [-x /usr/bin/id ]; then #记录当前登录用户的id     if [-z"$EUID"]; then         # ksh workaround         EUID=`id -u`         UID=`id -ru`     fi     USER="`id -un`" #记录登录用户名称     LOGNAME=$USER #设置登录用户名称     MAIL="/var/spool/mail/$USER" #设置用户邮箱地址 fi   # Path manipulation if ["$EUID"="0"]; then #超级用户环境变量     pathmunge /sbin     pathmunge /usr/sbin     pathmunge /usr/local/sbin else     pathmunge /usr/local/sbin after #普通用户环境变量     pathmunge /usr/sbin after     pathmunge /sbin after fi   HOSTNAME=`/bin/hostname 2>/dev/null` #定义主机名 HISTSIZE=1000                             #定义历史命令条数 if ["$HISTCONTROL"="ignorespace"] ; then     export HISTCONTROL=ignoreboth else     export HISTCONTROL=ignoredups fi   export PATH USER LOGNAME MAIL HOSTNAME HISTSIZE HISTCONTROL   # By default, we want umask to get set. This sets it for login shell # Current threshold for system reserved uid/gids is 200 # You could check uidgid reservation validity in # /usr/share/doc/setup-*/uidgid file if [$UID-gt199] && ["`id -gn`"="`id -un`"]; then #设置umask     umask002 else     umask022 fi   for i in /etc/profile.d/*.sh ; do #调用profile.d/下的所有shell     if [-r"$i"]; then         if ["${-#*i}"!="$-"]; then             . "$i"         else                                                                                                                                                                                                                                                             . "$i">/dev/null 2>&1                                                                                                                                                                                                                                  fi                                                                                                                                                                                                                                                       fi                                                                                                                                                                                                                                                       done                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      unset i                                                                                                                                                                                                                                                      unset-f pathmunge

 

Shell登录信息

本地终端欢迎信息：/etc/issue

\d	显示当前系统时间
\s	显示操作系统名称
\l	显示登录的终端号，
\m	显示硬件体系结构，比如i386, i686
\n	显示主机名
\o	显示域名
\r	显示内核版本
\t	显示当前系统时间
\u	显示当前登录用户序列号

 

远程终端欢迎信息：/etc/issus.net

a.     转译符不再生效

b.     是否显示欢迎信息，由ssh的配置文件/etc/ssh/sshd_config决定，加入”Banner/etc/issue.net”行才能显示（要重启ssh服务）

 

登录后的欢迎信息：/etc/motd

不管是本地登录，还是远程登录，都可以显示该欢迎信息