Bash Startup Files

When bash is started it runs a series of scripts to prepare the environment for user. These scripts, for example, set the environment variables, create command aliases, run programs.

There are two main types of a shell instance, interactive and noninteractive. However, noninteractive shells (such as those running shell scripts) usually don’t read any startup files. To run a noninteractive shell as a login shell, to force it to run startup files, start the shell with the -l or --login option.

Interactive shell can be a:

login shell - a shell started by the login program or a remote login server such as SSH (it’s startup files are a place for variables like PATH, PS1 and startup programs like umask)
non-login shell - additional shell you run after you log in - ex. shell inside an X-based terminal (it’s startup files are a place for aliases and functions)

… to find out run echo $0 | perl -lne 'print /^\-/ ? "" : "non-", "login shell"'

	Login shell	Non-login shell
Global config	`/etc/profile` (, `/etc/profile.d/`)	`/etc/bash.bashrc`, `/etc/bash/bashrc`, `/etc/bashrc`
User config	`~/.bash_profile`, `~/.bash_login`, `~/.profile` (only the first found is run)	`~/.bashrc`

Creating a symlink between ~/.bashrc and ~/.bash_profile will ensure that the same startup scripts run for both login and non-login sessions. Debian’s ~/.profile sources ~/.bashrc, which has the same effect.

Prostredie shellu (in Slovak)
my dot-files
ULSAH p. 189
How Linux Works, 2nd, ch. 13