bashrc

If you spend a lot of time on the command line, chances are that you’ll want to customize your shell environment. This can mean creating aliases, adding a new directory to the $PATH , or changing the look of the shell prompt.

You may have come across some tutorials where they say to put your configuration either in the .bashrc, .bash_profile or another configuration file that is read and executed by the bash shell.

Bash Startup Files

When invoked as an interactive login shell, Bash looks for the /etc/profile file, and if the file exists , it runs the commands listed in the file. Then Bash searches for _{/.bash_profile,} /.bash_login, and ~/.profile files, in the listed order, and executes commands from the first readable file found.

When Bash is invoked as an interactive non-login shell, it reads and executes commands from ~/.bashrc, if that file exists, and it is readable.

Difference Between .bashrc and .bash_profile

.bash_profile is read and executed when Bash is invoked as an interactive login shell, while .bashrc is executed for an interactive non-login shell.

Use .bash_profile to run commands that should run only once, such as customizing the $PATH environment variable .

Put the commands that should run every time you launch a new shell in the .bashrc file. This include your aliases and functions , custom prompts, history customizations , and so on.

Typically, ~/.bash_profile contains lines like below that source the .bashrc file. This means each time you log in to the terminal, both files are read and executed.

if [ -f ~/.bashrc ]; then
	. ~/.bashrc
fi

~/.profile and ~/.bash_profile

Most Linux distributions are using ~/.profile instead of _{/.bash_profile. The} /.profile file is read by all shells, while ~/.bash_profile only by Bash.

If any startup file is not present on your system, you can create it.

More

profile

profile，路徑：/etc/profile，用於設定係統級的環境變數和啟動程序，在此文件下配置對所有使用者生效。 當登入使用者（login）時，檔案會被執行，並從/etc/profile.d目錄的設定檔中找到shell設定。

bash_profile

bash_profile只對單一使用者有效，檔案儲存位於~/.bash_profile，該檔案是一個使用者層級的設置，可以理解為某個使用者的設定檔目錄下。

該文件也可以用於配置環境變數和啟動程序，但僅針對單一使用者有效。

和 profile 檔案類似，bash_profile 也可以在使用者登入（login）時生效，也可以用來設定環境變數。

但與 profile 不同，bash_profile 只能對目前使用者生效。

#BASH Alias BASH Alias is a shortcut to run commands using some mapping. It is a way to create some shortcut commands for repetitive and multiple tasks. We create an alias in a BASH environment in specified files. We can also incorporate BASH functions, variables, etc to make the Alias more programmatic and flexible.