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
A default TERM
value will be set on a per-line basis by either
(e.g., System-V-like UNIXes) or /etc/ttys
UNIXes). This will nearly always suffice for workstation and microcomputer
If you use a dialup line, the type of device attached to it may vary. Older UNIX
systems pre-set a very dumb terminal 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 emulators.
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
setting 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 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/misc/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
replace); to examine an entry, you must use the infocmp
Invoke it as follows:
is the name of the type you wish to examine (and the
name of its capability file the subdirectory of /usr/share/misc/terminfo named
for its first letter). This command dumps a capability file in the text format
described by terminfo
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
, 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 primary 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 letters or digits. You need to avoid using
punctuation characters in root names, because they are used and interpreted as
filenames and shell meta-characters (such as !, $, *, ?, etc.) embedded in
them may cause odd and unhelpful 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 terminals), or a common name of the
terminal line ( vt
for the VT series of terminals from DEC, or
for Sun Microsystems workstation consoles, or regent
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
The root name for a PC-Unix console type should be the OS name, i.e.,
. It should
or any other generic that might cause confusion
in a multi-platform environment! If a model number follows, 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
Following the root name, you may add any reasonable number of hyphen-separated
- Has two pages of memory. Likewise 4p, 8p, etc.
- 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
- Enable auto-margin (right-margin wraparound).
- Mono mode - suppress color support.
- No arrow keys - termcap ignores arrow keys which are actually there on the
terminal, so the user can use the arrow keys locally.
- No auto-margin - suppress am capability.
- No labels - suppress soft labels.
- No status line - suppress status line.
- Has a printer port which is used.
- Terminal in reverse video mode (black on white).
- Enable status line.
- Use visible bell (flash) rather than beep.
- 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
(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
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
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.
- compiled terminal capability data base
- tty line initialization (AT&T-like UNIXes)
- tty line initialization (BSD-like UNIXes)