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环境变量
环境变量是和 Shell 紧密相关的,用户登录系统后就启动了一个 Shell 。对于 Linux 来说一般是 bash ,但也可以重新设定或切换到其它的 Shell 。根据发行版本的情况, bash 有两个基本的系统级配置文件: /etc/bashrc 和 /etc/profile 。这些配置文件包含两组不同的变量: shell 变量和环境变量。前者只是在特定的 shell 中固定(如 bash ),后者在不同 shell 中固定。很明显, shell 变量是局部的,而环境变量是全局的。环境变量是通过 Shell 命令来设置的,设置好的环境变量又可以被所有当前用户所运行的程序所使用。对于 bash 这个 Shell 程序来说,可以通过变量名来访问相应的环境变量,通过 export 来设置环境变量
方法一:直接运行命令
代码如下 export PATH=$PATH:/usr/local/webserver/php/bin 和 export PATH=$PATH:/usr/local/webserver/mysql/bin使用这种方法,只会对当前会话有效,也就是说每当登出或注销系统以后,PATH 设置就会失效,只是临时生效。
方法二:执行vi ~/.bash_profile修改文件中PATH一行,将/usr/local/webserver/php/bin 和 /usr/local/webserver/mysql/bin 加入到PATH=$PATH:$HOME/bin一行之后
这种方法只对当前登录用户生效
方法三:修改/etc/profile文件使其永久性生效,并对所有系统用户生效,在文件末尾加上如下两行代码
PATH=$PATH:/usr/local/webserver/php/bin:/usr/local/webserver/mysql/bin
export PATH
[root@CentOS ~]# vi /etc/profile
在文件末尾加上如下两行代码
代码如下PATH=/usr/local/webserver/php/bin:$PATH
export PATH
# /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/$USER"
fi
# Path manipulation
if [ "$EUID" = "0" ]; then
pathmunge /sbin
pathmunge /usr/sbin
pathmunge /usr/local/sbin
else
pathmunge /usr/local/sbin after
pathmunge /usr/sbin after
pathmunge /sbin after
fi
HOSTNAME=`/bin/hostname 2>/dev/null`
HISTSIZE=1000
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 [ $UID -gt 199 ] && [ "`id -gn`" = "`id -un`" ]; then
umask 002
else
umask 022
fi
for i in /etc/profile.d/*.sh ; do
if [ -r "$i" ]; then
if [ "${-#*i}" != "$-" ]; then
. "$i"
else
. "$i" >/dev/null 2>&1
fi
fi
done
unset i
unset pathmunge
PATH=/usr/local/webserver/php/bin:$PATH
export PATH
要是刚才的修改马上生效,需要执行以下代码
[root@CentOS ~]# source /etc/profile
这时再查看系统环境变量,就能看见刚才加的东西已经生效了
[root@CentOS ~]# echo $PATH
/usr/local/webserver/php/bin:/usr/lib/qt-3.3/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin