49.4.3 Terminal-specific Initialization

Each terminal type can have a Lisp library to be loaded into Emacs when it is run on that type of terminal. For a terminal type named termtype, the library is called term/termtype. (If there is an entry of the form (termtype . alias) in the term-file-aliases association list, Emacs uses alias in place of termtype.) The library is found by searching the directories load-path as usual and trying the suffixes ‘ .elc’ and ‘ .el’. Normally it appears in the subdirectory term of the directory where most Emacs libraries are kept.

The usual purpose of the terminal-specific library is to map the escape sequences used by the terminal’s function keys onto more meaningful names, using input-decode-map. See the file term/lk201.el for an example of how this is done. Many function keys are mapped automatically according to the information in the Termcap data base; the terminal-specific library needs to map only the function keys that Termcap does not specify.

When the terminal type contains a hyphen, only the part of the name before the first hyphen is significant in choosing the library name. Thus, terminal types ‘ aaa-48’ and ‘ aaa-30-rv’ both use the library term/aaa. The code in the library can use (getenv "TERM") to find the full terminal type name.

The library’s name is constructed by concatenating the value of the variable term-file-prefix and the terminal type. Your .emacs file can prevent the loading of the terminal-specific library by setting term-file-prefix to nil.

Emacs runs the hook tty-setup-hook at the end of initialization, after both your .emacs file and any terminal-specific library have been read in. Add hook functions to this hook if you wish to override part of any of the terminal-specific libraries and to define initializations for terminals that do not have a library. See Hooks.