What Goes in Shell Setup Files? (Unix Power Tools, 3rd Edition)

3.5. What Goes in Shell Setup Files?

Setup files for login shells ( Section 3.4) -- such as .login and .profile -- typically do at least the following:

Set the search path (Section 27.6) if the system default path isn't what you want.
Set the terminal type (Section 5.3) and make various terminal settings (Section 5.7, Section 5.8) if the system might not know your terminal (if you log in from various terminals over a dialup line or from a terminal emulator on a desktop machine, for instance).
Set environment variables (Section 35.3) that might be needed by programs or scripts that you typically run.
Run one or more commands that you want to run whenever you log in. For example, if your system login program doesn't show the message of the day, your setup file can. Many people also like to print an amusing or instructive fortune. You also might want to run who (Section 2.8) or uptime (Section 26.4) or w (a combination of the other two, but not found on all systems) for information about the system.

In the C shell, the .cshrc file is used to establish settings that will apply to every instance of the C shell, not just login shells. For example, you typically want aliases (Section 28.2) available in every interactive shell you run -- but these aren't passed through the environment, so a setup file has to do the job. You may wish to put all of your aliases into another file, such as .aliases, or qualify the name with the shell's name, such as .csh.aliases, to allow for different alias formats between shells, and then you can use the source command to read in that file on startup from .cshrc.

Even novices can write simple setup files. The trick is to make these setup scripts really work for you. Here are some of the things you might want to try:

Creating a custom prompt.
Coordinating custom setup files on different machines (Section 3.18).
Making different terminal settings depending on which terminal you're using (Section 3.10 and others).
Seeing the message of the day only when it changes.
Doing all of the above without making your login take forever.

--TOR and SJC