Termcap

Termcap, short for terminal capability, is a legacy software interface used by Unix-like systems to describe the capabilities and control sequences of text terminals. It provides a portable way for programs to interact with diverse terminals without embedding terminal-specific codes in application code. Termcap entries describe how to perform common tasks such as clearing the screen, moving the cursor, and querying terminal size, via a shared library interface.

The data is stored in a text database, with one line per terminal type. Each entry begins with the terminal name, followed by a colon-separated list of capability tokens. Capabilities are grouped into booleans, numerics, and strings. Programs access them through helper functions such as tgetent, tgetflag, tgetnum, and tgetstr. Examples of commonly used capabilities include cl (clear screen), cm (cursor motion), co (number of columns), and li (number of lines). The is capability holds the initialization string, and tc may include the terminal type of another entry to enable inheritance.

Termcap originated in early Unix systems as the primary terminal-handling interface. It is closely associated with the curses library, which used termcap data to provide a higher-level screen-management API. Its format is human-readable, which made it stable for maintenance but less scalable than alternative schemes.

File locations typically include /etc/termcap or /usr/share/misc/termcap. In modern systems, terminfo has largely supplanted termcap, offering more robust data models and a compiled database. However, termcap remains relevant for legacy software and compatibility layers, and tools exist to convert between formats (for example, captoinfo).