7. Environment Variables¶

7.1. Paths¶

/etc/environment
/etc/profile
/etc/bashrc
~/.bashrc
~/.profile
/etc/alternatives/

7.2. Variables¶

$HOME - User Home Directory
$HOSTNAME - Hostname
$IFS - Inter Field Separator
$LANG - System Language
$PATH - Executable Search Path
$PS1 - Prompt
$PWD - Present Working Directory
$SHELL - Current Shell
$TERM - Current Terminal (character mapping)
$UID - User ID
$UMASK - Permission mask for new files
$USER - Username
$LANG -
$LS_COLORS -
$_ -

7.3. PS1¶

../../_images/bash-colors.png — Figure 7.3. Bash colors¶

# Colors
red='\[\033[00;31m\]'
green='\[\033[00;32m\]'
blue='\[\033[00;36m\]'
white='\[\033[00;39m\]'

# User Prompt
[ $UID != 0 ] && export PS1="\n${green}$ ${white}"

# Root Prompt
[ $UID == 0 ] && export PS1="\n${red}# ${white}"

# Remote Prompt
[ $SSH_CONNECTION ] && export PS1="\n${green}\h $ ${white}"

7.4. Commands¶

Table 7.1. Env¶
Command	Type	Description
`env`		Show all environmental variables
`env`		run a program in a modified environment
`update-alternatives`		maintain symbolic links determining default commands
`export`		Set environment variable