Master Linux Environment Variables: Six Ways to Set and Load PATH

Linux Environment Variable Configuration

When installing software you often need to set environment variables. Below are several methods to configure them on Ubuntu 14.04 for user uusama, adding MySQL's /home/uusama/mysql/bin to PATH.

Reading Environment Variables

Use export to list all variables and echo $PATH to show the current PATH value.

uusama@ubuntu:~$ export
declare -x HOME="/home/uusama"
declare -x LANG="en_US.UTF-8"
declare -x LANGUAGE="en_US:"
declare -x LESSCLOSE="/usr/bin/lesspipe %s %s"
declare -x LESSOPEN="| /usr/bin/lesspipe %s"
declare -x LOGNAME="uusama"
declare -x MAIL="/var/mail/uusama"
declare -x PATH="/home/uusama/bin:/home/uusama/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
declare -x SSH_TTY="/dev/pts/0"
declare -x TERM="xterm"
declare -x USER="uusama"

uusama@ubuntu:~$ echo $PATH
/home/uusama/bin:/home/uusama/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

The PATH variable contains colon‑separated directories searched for executables. When using export you may enclose the value in quotes or not.

Method 1: export PATH directly

export PATH=/home/uusama/mysql/bin:$PATH
# or prepend
export PATH=$PATH:/home/uusama/mysql/bin

Effective immediately

Only for the current terminal session

Applies to the current user

Remember to include the original $PATH to avoid overwriting existing entries

Method 2: edit ~/.bashrc

vim ~/.bashrc
# add at the end
export PATH=$PATH:/home/uusama/mysql/bin

Effective when a new terminal is opened or after running source ~/.bashrc Permanent for the user

Only affects the current user

May be overridden by later files that reset

PATH

Method 3: edit ~/.bash_profile

vim ~/.bash_profile
# add at the end
export PATH=$PATH:/home/uusama/mysql/bin

Effective after opening a new terminal or source ~/.bash_profile Permanent for the user

If ~/.bash_profile does not exist, edit ~/.profile instead

Method 4: edit /etc/bashrc (system‑wide)

# make file writable if needed
chmod -v u+w /etc/bashrc
vim /etc/bashrc
# add at the end
export PATH=$PATH:/home/uusama/mysql/bin

Effective in new terminals or after source /etc/bashrc Permanent

Applies to all users

Method 5: edit /etc/profile

# make file writable if needed
chmod -v u+w /etc/profile
vim /etc/profile
# add at the end
export PATH=$PATH:/home/uusama/mysql/bin

Effective in new terminals or after source /etc/profile Permanent

System‑wide

Method 6: edit /etc/environment

# make file writable if needed
chmod -v u+w /etc/environment
vim /etc/environment
# add at the end
export PATH=$PATH:/home/uusama/mysql/bin

Effective in new terminals or after source /etc/environment Permanent

System‑wide

How Linux Loads Environment Variables

Linux reads configuration files in a specific order, which determines which definition wins when the same variable appears multiple times.

Classification

User‑level files: ~/.bashrc, ~/.profile (or ~/.bash_profile)

System‑level files: /etc/bashrc, /etc/profile (or /etc/bash_profile), /etc/environment During login the shell reads ~/.bash_profile (or ~/.profile), then ~/.bashrc. If the former is missing, it falls back to ~/.bash_login.

Testing Load Order

By adding a line export UU_ORDER="$UU_ORDER:/path/to/file" to the first line of each file and then opening a new shell, the resulting value shows the load sequence:

$ echo $UU_ORDER
$UU_ORDER:/etc/environment:/etc/profile:/etc/bash.bashrc:/etc/profile.d/test.sh:~/.profile:~/.bashrc

The observed order is:

/etc/environment

/etc/profile

/etc/bash.bashrc

/etc/profile.d/test.sh

~/.profile

~/.bashrc

Detailed File Loading

/etc/profile

sources /etc/bash.bashrc and then iterates over /etc/profile.d/*.sh. The user’s ~/.profile subsequently sources ~/.bashrc. The ~/.profile is read only once at login, while ~/.bashrc is read for each interactive shell.

Tips

Create a project‑specific file (e.g., uusama.profile) and source it from ~/.profile to load custom variables automatically.

Define command aliases with alias rm="rm -i" in ~/.profile for safer usage.