Shell sessions

Types of shell session

Shell sessions can be one of or several instances of the following types:

  • login shell
    • A session that must be authenticated such as when you access remote resources using SSH
  • non-login shell
    • Not the above
  • interactive shell
    • A shell session that runs in the terminal and thus that the user can interact with
  • non-interactive shell
    • A shell session that runs without a terminal

If you are working with a remote server you will be in an interactive login shell. If you run a script from the command line you will be in a non-interactive non-login shell.

Shell sessions and access

The type of shell session that you are currently in affects the environmental and shell variables that you can access. This is because the order in which configuration files are read on initialisation differs depending on the type of shell.

  • a session defined as a non-login shell will read /etc/bash.bashrc and then the user-specific ~/.bashrc file to build its environment.
  • A session started as a login session will read configuration details from the /etc/profile file first. It will then look for the first login shell configuration file in the user’s home directory to get user-specific configuration details.

In Linux, if you want the environmental variable to be accessible from both login and non-login shells, you must put them in ~/.bashrc

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