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term

Section: Environments, Tables, and Troff Macros (7)
Index

NAME

term - conventions for naming terminal types

DESCRIPTION

The environment variable TERM should normally contain the type name ofthe terminal, console or display-device type you are using. This informationis critical for all screen-oriented programs, including your editor and mailer.

A default TERM value will be set on a per-line basis by either/etc/inittab (Linux and System-V-like UNIXes) or /etc/ttys (BSDUNIXes). This will nearly always suffice for workstation and microcomputerconsoles.

If you use a dialup line, the type of device attached to it may vary. OlderUNIX systems pre-set a very dumb terminal type like `dumb' or `dialup' ondialup lines. Newer ones may pre-set `vt100', reflecting the prevalence of DECVT100-compatible terminals and personal-computer emulators.

Modern telnets pass your TERM environment variable from the local side tothe remote one. There can be problems if the remote terminfo or termcap entryfor your type is not compatible with yours, but this situation is rare andcan almost always be avoided by explicitly exporting `vt100' (assuming youare in fact using a VT100-superset console, terminal, or terminal emulator.)

In any case, you are free to override the system TERM setting to yourtaste in your shell profile. The tset(1) utility may be of assistance;you can give it a set of rules for deducing or requesting a terminal type basedon the tty device and baud rate.

Setting your own TERM value may also be useful if you have created acustom entry incorporating options (such as visual bell or reverse-video)which you wish to override the system default type for your line.

Terminal type descriptions are stored as files of capability data underneath/usr/share/terminfo. To browse a list of all terminal names recognized by the system, do

toe | more

from your shell. These capability files are in a binary format optimized forretrieval speed (unlike the old text-based termcap format they replace);to examine an entry, you must use the infocmp(1M) command.Invoke it as follows:

infocmp entry-name

where entry-name is the name of the type you wish to examine (and thename of its capability file the subdirectory of /usr/share/terminfo named for its firstletter). This command dumps a capability file in the text format described byterminfo(5).

The first line of a terminfo(5) description gives the names by whichterminfo knows a terminal, separated by `|' (pipe-bar) characters with the lastname field terminated by a comma. The first name field is the type'sprimary name, and is the one to use when setting TERM. The lastname field (if distinct from the first) is actually a description of theterminal type (it may contain blanks; the others must be single words). Namefields between the first and last (if present) are aliases for the terminal,usually historical names retained for compatibility.

There are some conventions for how to choose terminal primary names that helpkeep them informative and unique. Here is a step-by-step guide to namingterminals that also explains how to parse them:

First, choose a root name. The root will consist of a lower-case letterfollowed by up to seven lower-case letters or digits. You need to avoid usingpunctuation characters in root names, because they are used and interpreted asfilenames and shell meta-characters (such as !, $, *, ?, etc.) embedded in themmay cause odd and unhelpful behavior. The slash (/), or any other characterthat may be interpreted by anyone's file system (\, $, [, ]), is especiallydangerous (terminfo is platform-independent, and choosing names with specialcharacters could someday make life difficult for users of a future port). Thedot (.) character is relatively safe as long as there is at most one per rootname; some historical terminfo names use it.

The root name for a terminal or workstation console type should almost alwaysbegin with a vendor prefix (such as hp for Hewlett-Packard, wy forWyse, or att for AT&T terminals), or a common name of the terminal line(vt for the VT series of terminals from DEC, or sun for SunMicrosystems workstation consoles, or regent for the ADDS Regent series.You can list the terminfo tree to see what prefixes are already in common use.The root name prefix should be followed when appropriate by a model number;thus vt100, hp2621, wy50.

The root name for a PC-Unix console type should be the OS name,i.e. linux, bsdos, freebsd, netbsd. It shouldnot be console or any other generic that might cause confusion in amulti-platform environment! If a model number follows, it should indicateeither the OS release level or the console driver release level.

The root name for a terminal emulator (assuming it does not fit one of thestandard ANSI or vt100 types) should be the program name or a readilyrecognizable abbreviation of it (i.e. versaterm, ctrm).

Following the root name, you may add any reasonable number of hyphen-separatedfeature suffixes.

2p: Has two pages of memory. Likewise 4p, 8p, etc.
mc: Magic-cookie. Some terminals (notably older Wyses) can only support oneattribute without magic-cookie lossage. Their base entry is usually pairedwith another that has this suffix and uses magic cookies to support multipleattributes.
-am: Enable auto-margin (right-margin wraparound).
-m: Mono mode - suppress color support.
-na: No arrow keys - termcap ignores arrow keys which are actually there on theterminal, so the user can use the arrow keys locally.
-nam: No auto-margin - suppress am capability.
-nl: No labels - suppress soft labels.
-nsl: No status line - suppress status line.
-pp: Has a printer port which is used.
-rv: Terminal in reverse video mode (black on white).
-s: Enable status line.
-vb: Use visible bell (flash) rather than beep.
-w: Wide; terminal is in 132 column mode.

Conventionally, if your terminal type is a variant intended to specify aline height, that suffix should go first. So, for a hypothetical FuBarComodel 2317 terminal in 30-line mode with reverse video, best form would befubar-30-rv (rather than, say, `fubar-rv-30').

Terminal types that are written not as standalone entries, but rather ascomponents to be plugged into other entries via use capabilities,are distinguished by using embedded plus signs rather than dashes.

Commands which use a terminal type to control display often accept a -Toption that accepts a terminal name argument. Such programs should fall backon the TERM environment variable when no -T option is specified.

PORTABILITY

For maximum compatibility with older System V UNIXes, names and aliasesshould be unique within the first 14 characters.

FILES

/usr/share/terminfo/?/*: compiled terminal capability data base
/etc/inittab: tty line initialization (AT&T-like UNIXes)
/etc/ttys: tty line initialization (BSD-like UNIXes)