term(7) term(7)
term - conventions for naming terminal types
The environment variable TERM should normally contain the
type name of the terminal, console or display-device type
you are using. This information is 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 (e.g., System-V-like UNIXes) or
/etc/ttys (BSD UNIXes). This will nearly always suffice
for workstation and microcomputer consoles.
If you use a dialup line, the type of device attached to
it may vary. Older UNIX systems pre-set a very dumb ter-
minal type like `dumb' or `dialup' on dialup lines. Newer
ones may pre-set `vt100', reflecting the prevalence of DEC
VT100-compatible terminals and personal-computer emula-
tors.
Modern telnets pass your TERM environment variable from
the local side to the remote one. There can be problems
if the remote terminfo or termcap entry for your type is
not compatible with yours, but this situation is rare and
can almost always be avoided by explicitly exporting
`vt100' (assuming you are in fact using a VT100-superset
console, terminal, or terminal emulator.)
In any case, you are free to override the system TERM set-
ting to your taste 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 based on
the tty device and baud rate.
Setting your own TERM value may also be useful if you have
created a custom entry incorporating options (such as vis-
ual bell or reverse-video) which you wish to override the
system default type for your line.
Terminal type descriptions are stored as files of capabil-
ity 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 for retrieval speed (unlike the old text-
based termcap format they replace); to examine an entry,
you must use the infocmp(1m) command. Invoke it as fol-
lows:
infocmp entry_name
where entry_name is the name of the type you wish to exam-
ine (and the name of its capability file the subdirectory
of /usr/share/terminfo named for its first letter). This
command dumps a capability file in the text format
described by terminfo(5).
The first line of a terminfo(5) description gives the
names by which terminfo knows a terminal, separated by `|'
(pipe-bar) characters with the last name field terminated
by a comma. The first name field is the type's primary
name, and is the one to use when setting TERM. The last
name field (if distinct from the first) is actually a
description of the terminal type (it may contain blanks;
the others must be single words). Name fields 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 pri-
mary names that help keep them informative and unique.
Here is a step-by-step guide to naming terminals that also
explains how to parse them:
First, choose a root name. The root will consist of a
lower-case letter followed by up to seven lower-case let-
ters or digits. You need to avoid using punctuation char-
acters in root names, because they are used and inter-
preted as filenames and shell meta-characters (such as !,
$, *, ?, etc.) embedded in them may cause odd and unhelp-
ful behavior. The slash (/), or any other character that
may be interpreted by anyone's file system (\, $, [, ]),
is especially dangerous (terminfo is platform-independent,
and choosing names with special characters could someday
make life difficult for users of a future port). The dot
(.) character is relatively safe as long as there is at
most one per root name; some historical terminfo names use
it.
The root name for a terminal or workstation console type
should almost always begin with a vendor prefix (such as
hp for Hewlett-Packard, wy for Wyse, or att for AT&T ter-
minals), or a common name of the terminal line (vt for the
VT series of terminals from DEC, or sun for Sun Microsys-
tems workstation consoles, or regent for the ADDS Regent
series. You can list the terminfo tree to see what pre-
fixes 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 should not
be console or any other generic that might cause confusion
in a multi-platform environment! If a model number fol-
lows, it should indicate either the OS release level or
the console driver release level.
The root name for a terminal emulator (assuming it does
not fit one of the standard ANSI or vt100 types) should be
the program name or a readily recognizable abbreviation of
it (i.e., versaterm, ctrm).
Following the root name, you may add any reasonable number
of hyphen-separated feature suffixes.
2p Has two pages of memory. Likewise 4p, 8p, etc.
mc Magic-cookie. Some terminals (notably older Wyses)
can only support one attribute without magic-cookie
lossage. Their base entry is usually paired with
another that has this suffix and uses magic cookies
to support multiple attributes.
-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 the terminal, 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 a line height, that suffix should go
first. So, for a hypothetical FuBarCo model 2317 terminal
in 30-line mode with reverse video, best form would be
fubar-30-rv (rather than, say, `fubar-rv-30').
Terminal types that are written not as standalone entries,
but rather as components 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 -T option that accepts a terminal name
argument. Such programs should fall back on the TERM
environment variable when no -T option is specified.
For maximum compatibility with older System V UNIXes,
names and aliases should be unique within the first 14
characters.
/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)
curses(3x), terminfo(5), term(5).
term(7)