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.
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