etctermcap

etctermcap refers to the terminal capability database used by older Unix-like systems, typically stored in the file /etc/termcap. It provides descriptions of terminal types and their capabilities so applications can control terminal I/O in a device-independent way. The database is used by programs and libraries that implement the termcap interface to determine how to move the cursor, clear the screen, interpret key presses, and perform other terminal operations.

Format and contents

In a termcap file, each line defines a terminal type. The line starts with the terminal name (and optional aliases) followed by a colon, and then a sequence of capability fields separated by colons. Capabilities are categorized as boolean (present or absent), numeric (such as the number of columns or lines), or string (escape sequences or parameterized strings for actions like clearing the screen or moving the cursor). Examples of commonly defined capabilities include co for columns, li for lines, am for automatic margins, cl for clear screen, and cm for cursor addressing. The actual content consists of terminal-specific codes and escape sequences that tell software how to perform these actions on that terminal.

Relation to termcap and terminfo

Termcap is an early, human-readable database designed for simplicity and broad compatibility. Terminfo is a later, more flexible and compact database that uses a compiled binary format for faster access and a different naming scheme for capabilities. Many systems maintain compatibility with /etc/termcap, but modern distributions typically rely on the terminfo database located under /usr/share/terminfo, accessed through libraries such as ncurses. Some systems provide both, allowing legacy software to function while benefiting from a more robust terminal description framework.

Example and maintenance

An entry might look like: vt100:co#80:li#24:cl=...:cm=.... The exact sequences depend on the terminal. /etc/termcap is usually maintained by the operating system’s package manager for compatibility, though administrators may edit it for custom terminal devices. For new software and terminals, terminfo is commonly preferred.