Question

How to set environment variables

Asked by: yongsing

How do you set the PATH, JAVA_HOME or CLASSPATH in Redhat Linux?

I want to know how to set it such that when the OS is booted up, these variables are set. In Windows, this is done in the Control Panel -> System -> Advance -> Environment Variables.

I also want to know how you override the default variables in a particular shell. In Windows, we can do SET PATH=%PATH%;c:\newpath to override the default PATH.

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Asked On
2004-02-24 at 01:51:52ID20895782
Tags

linux

,

environment

,

set

,

variable

Topics

Linux

,

Linux Distributions

Participating Experts
5
Points
150
Comments
17

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Answers

 

by: da99rmdPosted on 2004-02-24 at 02:24:09ID: 10439635

if you are using bash
export JAVA_HOME="/usr/java/jdk1.3.1_01"

and if you are using tcsh
setenv JAVA_HOME /usr/java/jdk1.3.1_01

to Add a extra path do this in bash
export PATH=$PATH:/hejsan

 

by: da99rmdPosted on 2004-02-24 at 02:27:48ID: 10439654

sry didnt read the the middle questione

put that in /etc/bashrc if bash

and /etc/csh.login for tcsh

this applays to all users if you just want i to your self put only in

%HOME%/.bashrc or
%HOME%/.tcshrc

 

by: da99rmdPosted on 2004-02-24 at 02:29:23ID: 10439661

type
env
to see what your env settings are and what shell you are using under SHELL

/Rob

 

by: majorwooPosted on 2004-02-24 at 08:03:46ID: 10441949

da99rmd is right, another way is if you are setting this up for multiple users it can set in /etc/profile and it will be set for all system users at bootup

 

by: yongsingPosted on 2004-02-24 at 17:23:10ID: 10446773

I am using bash. Should I edit /etc/bashrc or etc/profile?

How do I add the settings in the file? This is how /etc/bashrc looks like:


# /etc/bashrc

# System wide functions and aliases
# Environment stuff goes in /etc/profile

# by default, we want this to get set.
# Even for non-interactive, non-login shells.
if [ "`id -gn`" = "`id -un`" -a `id -u` -gt 99 ]; then
      umask 002
else
      umask 022
fi

# are we an interactive shell?
if [ "$PS1" ]; then
    if [ -x /usr/bin/tput ]; then
      if [ "x`tput kbs`" != "x" ]; then # We can't do this with "dumb" terminal
        stty erase `tput kbs`
      elif [ -x /usr/bin/wc ]; then
        if [ "`tput kbs|wc -c `" -gt 0 ]; then # We can't do this with "dumb" terminal
          stty erase `tput kbs`
        fi
      fi
    fi
    case $TERM in
      xterm*)
            if [ -e /etc/sysconfig/bash-prompt-xterm ]; then
                  PROMPT_COMMAND=/etc/sysconfig/bash-prompt-xterm
            else
                PROMPT_COMMAND='echo -ne "\033]0;${USER}@${HOSTNAME%%.*}:${PWD/#$HOME/~}\007"'
            fi
            ;;
      screen)
            if [ -e /etc/sysconfig/bash-prompt-screen ]; then
                  PROMPT_COMMAND=/etc/sysconfig/bash-prompt-screen
            else
            PROMPT_COMMAND='echo -ne "\033_${USER}@${HOSTNAME%%.*}:${PWD/#$HOME/~}\033\\"'
            fi
            ;;
      *)
            [ -e /etc/sysconfig/bash-prompt-default ] && PROMPT_COMMAND=/etc/sysconfig/bash-prompt-default
          ;;
    esac
    # Turn on checkwinsize
    shopt -s checkwinsize
    [ "$PS1" = "\\s-\\v\\\$ " ] && PS1="[\u@\h \W]\\$ "
   
    if [ "x$SHLVL" != "x1" ]; then # We're not a login shell
        for i in /etc/profile.d/*.sh; do
          if [ -r "$i" ]; then
              . $i
          fi
      done
    fi
fi
# vim:ts=4:sw=4

 

by: jdfoxPosted on 2004-02-24 at 18:06:55ID: 10446991

The global /etc/profile and your own local  ~/.bash_profile are read when the shell is invoked as an interactive login shell, for example when you open a remote terminal session to someone else's machine, or when you log into your own machine without X Windows running, or when you hit ctrl-alt-F1 from X Windows to start a virtual terminal session.

The global /etc/bashrc (if it exists) and your own local  ~/.bashrc is read when the shell is invoked as an interactive non-login shell, for example when you open up a terminal window in Gnome or KDE.

So it sounds like you'll be wanting it in your /etc/bashrc if you want to set it for all users, or in your ~/.bashrc if it's just for you.

 

by: yongsingPosted on 2004-02-24 at 19:09:32ID: 10447344

This sounds really confusing. I just need to know the Linux's equivalent to Windows setting via Control Panel -> System -> Advance -> Environment Variables.

It would be good if you can show me what to add to the relevant file.

 

by: jdfoxPosted on 2004-02-24 at 19:37:26ID: 10447439

edit your ~/.bashrc with your favourite editor
add those export commands to the end of the file, that da99rmd told you about up in his first post.  
save, exit the editor.  
log out, log back in.

 

by: majorwooPosted on 2004-02-24 at 20:09:19ID: 10447573

/etc/profile
would be more akin to env variables in windows (as /etc/profile is independent of shell choices)

to set something in /etc/profile you simply do:

VARIABLE_NAME=VALUE_YOU_WANT_IT_TO_BE

and then add to the export line the variable name giving you something like:

export PATH USER VARIABLE_NAME

if you don't want to reboot (or log in/out) you can then type:
source /etc/profile

for all practical purposes though, for a one user system ~/.bashrc is the same

 

by: paullamhkgPosted on 2004-02-24 at 20:28:30ID: 10447639

majorwoo all show you the way, only that you have to login/get into a console mode (dos mode like) and use your editor to edit the file /etc/profile as majorwoo suggested.

and you have to login as root (the super user of linux/unix)

 

by: da99rmdPosted on 2004-02-24 at 23:57:14ID: 10448410

Im not realy in to windows but if the settings you are talking about in control pannel apply to all users or you want it to work that way put it in

/etc/bashrc

And if you just want the settings to the user you are using put it in your home directory in the file

.bashrc

/Rob

 

by: jdfoxPosted on 2004-02-25 at 06:54:35ID: 10450833

In Windows you open up a graphical dialogue, & click the "environment variables" button.  In there you can set variables for all users (known in MS Windows as "system variables") or just for the currently logged-in user ("user variables" in Windows)

There's only one right way to do it in MS Windows. It doesn't always work, but at least you know you tried the right thing. :-)

With Linux you gain the freedom to do it different ways, but at the price of reading lots of turgid manuals, and learning the several ways to configure things.  It might seem like a pain at first to learn this stuff, yongsing, but it's definitely worth it in the end.

 

by: majorwooPosted on 2004-02-25 at 07:54:53ID: 10451429

da99rmd,

/etc/bashrc woud apply to all users using the bash shell (which is indeed the default for many linux systems) however if a user is using a different shell /etc/bashrc would be ignored.  Take a look at your /etc/passwd file, you will see  something like:
guest:x:509:500::/home/guest:/bin/bash
indicating the user guest, uses the bash shell.  If this here changed (if the user used a different shell such as /bin/csh, or alternatively if they launched their own new shell once logging in anythign entered in /etc/bashrc would not be read by that shell)

/etc/profile on the other hand is read by all user shells regardless of what the user has set

 

by: da99rmdPosted on 2004-02-26 at 00:52:13ID: 10458270

jdfox, but then you end up lerning somthing on the way when you are using linux :)

majorwoo, thats correct but most users dont chsh :/

 

by: majorwooPosted on 2004-02-26 at 04:56:17ID: 10459685

for sure, I'm just arguing principle now.  It "is" closer to the windows way ;-)

 

by: yongsingPosted on 2004-02-27 at 00:26:27ID: 10467428

Thanks guys!

 

by: dcrawford999Posted on 2004-06-25 at 11:41:29ID: 11401329

Modify the file /etc/csh.login

something like this:

setenv PATH ".:/bin:/usr/bin:/usr/local/bin"   <--note the . which sets up local dir in path

setenv JAVA_HOME "/opt/myjava"


to edit that path later use the following:

setenv PATH ".:${PATH}:/somewhere/new"

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