View and add environment variables under Linux

Source: Internet
Author: User

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$PATH: determines which directories the shell will look for commands or programs, the value of PATH is a series of directories, and when you run a program, Linux searches for compiled links in these directories.

Edit your PATH declaration in the following format:

Path= $PATH: <path 1>:<path 2>:<path 3>:------: <path n>

You can add the specified path yourself, separated by a colon. When the environment variable is changed, it takes effect the next time the user logs on, and if you want to take effect immediately, you can execute the following statement: $ source. bash_profile

It is important to note that it is best not to put the current path "./" in path, which may be subject to unexpected attacks. When you are finished, you can view the current search path through the echo $PATH. With this customization, you can avoid frequent launches of programs that are outside the path of the shell search.

1. Use the Export command to view the path value

[Email protected] u-boot-sh4]#Export
Declare-x cvs_rsh= "SSH"
Declare-x display= ": 0.0"
Declare-x g_broken_filenames= "1"
Declare-x histsize= "1000"
Declare-x home= "/root"
Declare-x hostname= "localhost"
Declare-x inputrc= "/ETC/INPUTRC"
Declare-x lang= "ZH_CN. UTF-8 "
Declare-x lessopen= "|/usr/bin/"
Declare-x logname= "Root"
Declare-x ls_colors= "no=00:fi=00:di=00;34:ln=00;36:pi=40;33:so=00;35:bd=40;33;01:cd=40;33;01:or=01;05;37;41:mi= 01;05;37;41:ex=00;32:*.cmd=00;32:*.exe=00;32:*.com=00;32:*.btm=00;32:*.bat=00;32:*.sh=00;32:*.csh=00;32:*.tar= 00;31:*.tgz=00;31:*.arj=00;31:*.taz=00;31:*.lzh=00;31:*.zip=00;31:*.z=00;31:*. z=00;31:*.gz=00;31:*.bz2=00;31:*.bz=00;31:*.tz=00;31:*.rpm=00;31:*.cpio=00;31:*.jpg=00;35:*.gif=00;35:*.bmp=00 ; 35:*.xbm=00;35:*.xpm=00;35:*.png=00;35:*.tif=00;35: "
Declare-x mail= "/var/spool/mail/root"
Declare-x oldpwd= "/root"
Declare-xPATH= "/usr/kerberos/sbin:/usr/kerberos/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"
Declare-x pwd= "/opt/stm/stlinux-2.3/devkit/sources/u-boot/u-boot-sh4"
Declare-x shell= "/bin/bash"
Declare-x shlvl= "1"
Declare-x ssh_askpass= "/usr/libexec/openssh/gnome-ssh-askpass"
Declare-x term= "Xterm"
Declare-x user= "Root"
Declare-x xauthority= "/root/.xauthkszh7b"

2. View the PATH environment variables separately, as available:

[Email protected] u-boot-sh4]#echo $PATH

3. Add the PATH environment variable (temporary), available:

[Email protected] u-boot-sh4]#export path=/opt/stm/stlinux-2.3/devkit/sh4/bin: $PATH

Check again:

[Email protected] u-boot-sh4]# echo $PATH
/opt/stm/stlinux-2.3/devkit/sh4/bin:/usr/kerberos/sbin:/usr/kerberos/bin:/usr/local/sbin:/usr/local/bin:/sbin :/bin:/usr/sbin:/usr/bin:/root/bin

Description Add path succeeded.

The path of the above method disappears after the terminal is closed.

4. Permanently add environment variable (affects current user)

#vim ~/.bashrcexport path= "/opt/stm/stlinux-2.3/devkit/sh4/bin: $PATH" 5. Permanently add environment variables (affects all users)# Vim/etc/profile at the end of the document, add:Export path= "/opt/stm/stlinux-2.3/devkit/sh4/bin: $PATH" Save, Exit, and run: # Source/etc/profile

No error is successful.

Questions :

1. Do the experiment, in/etc/profile, ~/.profile, ~/.BASHRC Add new path, restart all have no effect, only use source can, ubunt12.04

Find the cause, ~/.ZSHRC, because the path is re-assigned in ZSHRC without inheriting the previous $path, which causes the path to be re-assigned after the/etc/profile is loaded.

View and add environment variables under Linux

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