term(7)term(7)NAMEterm - conventions for naming terminal types
DESCRIPTION
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 (Linux and 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 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 format
they replace); to examine an entry, you must use the infocmp(1)
command. Invoke it as follows:
infocmp entry-name
where entry-name 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(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 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 sun for Sun
Microsystems 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 should not be console 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, 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 stand-alone 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.
PORTABILITY
For maximum compatibility with older System V UNIXes, names and aliases
should be unique within the first 14 characters.
FILES
/usr/share/misc/terminfo/?/*
compiled terminal capability database
/etc/inittab
tty line initialization (AT&T-like UNIXes)
/etc/ttys
tty line initialization (BSD-like UNIXes)
SEE ALSOcurses(3), terminfo(5), term(5).
March 1, 2011
