Environment
- Shell maintains lot of information during our shell session called the environment
- Programs/applications can use the data stored in this environment to determine info about system’s configuration.
- In this series
- printenv
- set
- export
- alias
What gets stored in Environment?
- Two types of data gets stored in the environment
- environment variables
- shell variables
- In addition to above mentioned variables shell stores
- aliases
- shell functions
Examine the Environment
- Execute the following command
printenv|less
printenv USER
printenv PATH
- Now lets execute one more comand
set | less
echo $HOME
- printenv command shows only environmental variables where set command displays both environment and shell variables
- we can print variables by adding $ to the varaible name
- Neither printenv nor set commands show aliases for that we need use command alias
Some Interesting Variables
- SHELL: The name of your shell program
- HOME: The path of your home directory
- LANG: Defines the character set
- OLDPWD: Previous working directory
- PATH: A colon-separated list of directories that are searched when you enter the name of a executable program
- USER: Your username
How is this Environment established
- When we login into linux system, bash program starts and reads series of configuration scripts called as start up files
- The exact sequence of files depends on type of shell you have started. There are two types
- Login shell session: This is the one in which we are prompted for username & password (ssh)
- A non-login shell: This generally occurs when we launch a terminal in GUI.
- Login shell session: This is the one in which we are prompted for username & password (ssh)