Types of Global Customization

The best possible approach to globally available customization would be a system-wide environment file that is separate from each user's environment file—just like /etc/profile is separate from each user's .bash_profile. Unfortunately, bash doesn't have this feature.

Nevertheless, the shell gives you a few ways to set up customizations that are available to all users at all times. Environment variables are the most obvious; your /etc/profile file will undoubtedly contain definitions for several of them, including PATH and TERM.

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The variable TMOUT is useful when your system supports dialup lines. Set it to a number N, and if a user doesn't enter a command within N seconds after the shell last issued a prompt, the shell will terminate. This feature is helpful in preventing people from "hogging" the dialup lines.

You may want to include some more complex customizations involving environment variables, such as the prompt string PS1 containing the current directory (as seen in Chapter 4).

You can also turn on options, such as emacs or vi editing modes, or noclobber to protect against inadvertent file overwriting. Any shell scripts you have written for general use also contribute to customization.

Unfortunately, it's not possible to create a global alias. You can define aliases in /etc/profile, but there is no way to make them part of the environment so that their definitions will propagate to subshells. (In contrast, users can define global aliases by putting their definitions in ~/.bashrc.)

However, you can set up global functions. These are an excellent way to customize your system's environment, because functions are part of the shell, not separate processes.

 

[8] If you are comfortable with Boolean logic, think of the umask as a number that the operating system logically ANDs with the permission given by the creating process.

[10] The "hard" and "soft" arguments are not available in bash prior to version 2.05a.