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5. Basic Concepts About Termcap and Terminfo

The file /etc/termcap is a text file that lists the terminal capabilities. Several applications use the termcap information to move the cursor around the screen and do other screen-oriented tasks. tcsh, bash, vi and all the curses-based applications use the termcap database.

The database describes several terminal types. The TERM environment variable selects the right behaviour at run-time, by naming a termcap entry to be used by applications.

Within the database, each capability of the terminal appears as a two-letter code and a representation of the actual escape sequence used to get the desired effect. The separator character between different capabilities is the colon (":"). As an example, the audible bell, with code "bl", usually appears as "bl=^G". This sequence tells that the bell sound is obtained by printing the control-G character, the ASCII BEL.

In addition to the bl capability, the vb capability is recognized. It is used to represent the "visible bell". vb is usually missing in the linux entry of the termcap file.

Most modern applications and libraries use the terminfo database instead of termcap. This database uses one file per terminal-type and lives in /usr/lib/terminfo; to avoid using huge directories, the description of each terminal type is stored in a directory named after its first letter; the linux entry, therefore, is /usr/lib/terminfo/l/linux. To build a terminfo entry you'll ``compile'' the termcap description; refer to the tic program and its manual page.