termcap(5) termcap(5)
NAME
termcap - terminal capability data base
SYNOPSIS
/etc/termcap
DESCRIPTION
termcap is a data base describing terminals used, e.g., by
vi(1). Terminals are described in termcap by giving a set
of capabilities which they have, and by describing how
operations are performed. Padding requirements and
initialization sequences are included in termcap.
Entries in termcap consist of a number of ``:'' separated
fields. The first entry for each terminal gives the names
which are known for the terminal, separated by ``|''
characters. The first name is always 2 characters long and
is used by older version 6 systems which store the terminal
type in a 16 bit word in a systemwide data base. The second
name given is the most common abbreviation for the terminal,
and the last name given should be a long name fully
identifying the terminal. The second name should contain no
blanks; the last name may well contain blanks for
readability.
CAPABILITIES
(P) indicates padding may be specified
(P*) indicates that padding may be based on no. lines affected
Name Type Pad? Description
ae str (P) End alternate character set
al str (P*) Add new blank line
am bool Terminal has automatic margins
as str (P) Start alternate character set
bc str Backspace if not CONTROL-h
bs bool Terminal can backspace with CONTROL-h
bt str (P) Back tab
bw bool Backspace wraps from column 0 to last column
CC str Command character in prototype if terminal settable
cd str (P*) Clear to end of display
ce str (P) Clear to end of line
ch str (P) Like cm but horizontal motion only, line stays same
cl str (P*) Clear screen
cm str (P) Cursor motion
co num Number of columns in a line
cr str (P*) Carriage return, (default CONTROL-m)
cs str (P) Change scrolling region (vt100), like cm
cv str (P) Like ch but vertical only.
da bool Display may be retained above
dB num Number of millisec of bs delay needed
db bool Display may be retained below
dC num Number of millisec of cr delay needed
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dc str (P*) Delete character
dF num Number of millisec of ff delay needed
dl str (P*) Delete line
dm str Delete mode (enter)
dN num Number of millisec of nl delay needed
do str Down one line
dT num Number of millisec of tab delay needed
ed str End delete mode
ei str End insert mode; give :ei=: if ic
eo str Can erase overstrikes with a blank
ff str (P*) Hardcopy terminal page eject (default CONTROL-l)
hc bool Hardcopy terminal
hd str Half-line down (forward 1/2 linefeed)
ho str Home cursor (if no cm)
hu str Half-line up (reverse 1/2 linefeed)
hz str Hazeltine; can't print ~'s
ic str (P) Insert character
if str Name of file containing is
im str Insert mode (enter); give :im=: if ic
in bool Insert mode distinguishes nulls on display
ip str (P*) Insert pad after character inserted
is str Terminal initialization string
k0-k9 str Sent by ``other'' function keys 0-9
kb str Sent by backspace key
kd str Sent by terminal down arrow key
ke str Out of ``keypad transmit'' mode
kh str Sent by home key
kl str Sent by terminal left arrow key
kn num Number of ``other'' keys
ko str Termcap entries for other non-function keys
kr str Sent by terminal right arrow key
ks str Put terminal in ``keypad transmit'' mode
ku str Sent by terminal up arrow key
l0-l9 str Labels on ``other'' function keys
li num Number of lines on screen or page
ll str Last line, first column (if no cm)
ma str Arrow key map, used by vi version 2 only
mi bool Safe to move while in insert mode
ml str Memory lock on above cursor.
ms bool Safe to move while in standout and underline mode
mu str Memory unlock (turn off memory lock).
nc bool No correctly working carriage return (DM2500,H2000)
nd str Non-destructive space (cursor right)
nl str (P*) Newline character (default \n)
ns bool Terminal is a CRT but doesn't scroll.
os bool Terminal overstrikes
pc str Pad character (rather than null)
pt bool Has hardware tabs (may need to be set with is)
se str End stand out mode
sf str (P) Scroll forwards
sg num Number of blank chars left by so or se
so str Begin stand out mode
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sr str (P) Scroll reverse (backwards)
ta str (P) Tab (other than CONTROL-i or with padding)
tc str Entry of similar terminal - must be last
te str String to end programs that use cm
ti str String to begin programs that use cm
uc str Underscore one char and move past it
ue str End underscore mode
ug num Number of blank chars left by us or ue
ul bool Terminal underlines even though it doesn't
overstrike
up str Upline (cursor up)
us str Start underscore mode
vb str Visible bell (may not move cursor)
ve str Sequence to end open/visual mode
vs str Sequence to start open/visual mode
xb bool Beehive (f1=escape, f2=ctrl C)
xn bool A newline is ignored after a wrap (Concept)
xr bool Return acts like ce \r \n (Delta Data)
xs bool Standout not erased by writing over it (HP 264?)
xt bool Tabs are destructive, magic so char (Teleray 1061)
A Sample Entry
The following entry, which describes the Concept-100, is
among the more complex entries in the termcap file as of
this writing. (This particular concept entry is outdated
and is used as an example only.)
c1 c100
concept100:is=\EU\Ef\E7\E5\E8\El\ENH\EK\E\200\Eo&\200:\
:al=3*\ECONTROL-R:am:bs:cd=16*\E^C:ce=16\E^S:cl=2*^L.br
:cm=\Ea%+ %+ :co#80:\ :dc=16\ECONTROL-A:dl=3*\E^B.br
:ei=\E\200:eo:im=\E^P:in:ip=16*:li#24:mi:nd=\E=:\
:se=\Ed\Ee:so=\ED\EE:ta=8\t:ul:up=\E;:vb=\Ek\EK:xn:
Entries may continue onto multiple lines by giving a \ as
the last character of a line, and that empty fields may be
included for readability (here between the last field on a
line and the first field on the next). Capabilities in
termcap are of three types: Boolean capabilities which
indicate that the terminal has some particular feature,
numeric capabilities giving the size of the terminal or the
size of particular delays, and string capabilities, which
give a sequence which can be used to perform particular
terminal operations.
Types of Capabilities
All capabilities have two letter codes. For instance, the
fact that the Concept has automatic margins (i.e. an
automatic return and linefeed when the end of a line is
reached) is indicated by the capability am. Hence the
description of the Concept includes am. Numeric
capabilities are followed by the character `#' and then the
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value. Thus co which indicates the number of columns the
terminal has gives the value `80' for the Concept.
Finally, string valued capabilities, such as ce (clear to
end of line sequence) are given by the two character code,
an `=', and then a string ending at the next following `:'.
A delay in milliseconds may appear after the `=' in such a
capability, and padding characters are supplied by the
editor after the remainder of the string is sent to provide
this delay. The delay can be either a integer, e.g. `20',
or an integer followed by an `*', i.e. `3*'. A `*'
indicates that the padding required is proportional to the
number of lines affected by the operation, and the amount
given is the per-affected-unit padding required. When a
``*'' is specified, it is sometimes useful to give a delay
of the form ``3.5'' specify a delay per unit to tenths of
milliseconds.
A number of escape sequences are provided in the string
valued capabilities for easy encoding of characters there.
A \E maps to an ESCAPE character, CONTROL-x maps to a
CONTROL-x for any appropriate x, and the sequences \n \r \t
\b \f give a newline, return, tab, backspace and formfeed.
Finally, characters may be given as three octal digits after
a \, and the characters CONTROL- and \ may be given as \^
and \\. If it is necessary to place a : in a capability it
must be escaped in octal as \072. If it is necessary to
place a null character in a string capability it must be
encoded as \200. The routines which deal with termcap use C
strings, and strip the high bits of the output very late so
that a \200 comes out as a \000 would.
Preparing Descriptions
We now outline how to prepare descriptions of terminals.
The most effective way to prepare a terminal description is
by imitating the description of a similar terminal in
termcap and to build up a description gradually, using
partial descriptions with ex to check that they are correct.
Be aware that a very unusual terminal may expose
deficiencies in the ability of the termcap file to describe
it or bugs in ex. To easily test a new terminal description
you can set the environment variable TERMCAP to a pathname
of a file containing the description you are working on and
the editor will look there rather than in /etc/termcap.
TERMCAP can also be set to the termcap entry itself to avoid
reading the file when starting up the editor. (This only
works on version 7 systems.)
Basic capabilities
The number of columns on each line for the terminal is given
by the co numeric capability. If the terminal is a CRT,
then the number of lines on the screen is given by the li
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capability. If the terminal wraps around to the beginning
of the next line when it reaches the right margin, then it
should have the am capability. If the terminal can clear
its screen, then this is given by the cl string capability.
If the terminal can backspace, then it should have the bs
capability, unless a backspace is accomplished by a
character other than CONTROL-h (ugh) in which case you
should give this character as the bc string capability. If
it overstrikes (rather than clearing a position when a
character is struck over) then it should have the os
capability.
A very important point here is that the local cursor motions
encoded in termcap are undefined at the left and top edges
of a CRT terminal. The editor will never attempt to
backspace around the left edge, nor will it attempt to go up
locally off the top. The editor assumes that feeding off
the bottom of the screen will cause the screen to scroll up,
and the am capability tells whether the cursor sticks at the
right edge of the screen. If the terminal has switch
selectable automatic margins, the termcap file usually
assumes that this is on, i.e. am.
These capabilities suffice to describe hardcopy and glass-
tty terminals. Thus the model 33 teletype is described as
t3|33|tty33:co#72:os
while the Lear Siegler ADM-3 is described as
cl|adm3|3|lsi adm3:am:bs:cl=CONTROL-Z:li#24:co#80
Cursor addressing
Cursor addressing in the terminal is described by a cm
string capability, with printf(3S) like escapes %x in it.
These substitute to encodings of the current line or column
position, while other characters are passed through
unchanged. If the cm string is thought of as being a
function, then its arguments are the line and then the
column to which motion is desired, and the % encodings have
the following meanings:
%d as in printf, 0 origin
%2 like %2d
%3 like %3d
%. like %c
%+x adds x to value, then %.
%>xy if value > x adds y, no output.
%r reverses order of line and column, no output
%i increments line/column (for 1 origin)
%% gives a single %
%n exclusive or row and column with 0140 (DM2500)
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%B BCD (16*(x/10)) + (x%10), no output.
%D Reverse coding (x-2*(x%16)), no output. (Delta Data).
Consider the HP2645, which, to get to row 3 and column 12,
needs to be sent \E&a12c03Y padded for 6 milliseconds. Note
that the order of the rows and columns is inverted here, and
that the row and column are printed as two digits. Thus its
cm capability is ``cm=6\E&%r%2c%2Y.'' The Microterm ACT-IV
needs the current row and column sent preceded by a
CONTROL-t, with the row and column simply encoded in binary,
``cm=CONTROL-T%.%.''. Terminals which use ``%.'' need to be
able to backspace the cursor (bs or bc), and to move the
cursor up one line on the screen (up introduced below).
This is necessary because it is not always safe to transmit
\t, \n CONTROL-d and \r, as the system may change or discard
them.
A final example is the LSI ADM-3a, which uses row and column
offset by a blank character, thus ``cm=\E=%+ %+'' .
Cursor motions
If the terminal can move the cursor one position to the
right, leaving the character at the current position
unchanged, then this sequence should be given as nd (non-
destructive space). If it can move the cursor up a line on
the screen in the same column, this should be given as up.
If the terminal has no cursor addressing capability, but can
home the cursor (to very upper left corner of screen) then
this can be given as ho; similarly a fast way of getting to
the lower left hand corner can be given as ll; this may
involve going up with up from the home position, but the
editor will never do this itself (unless ll does) because it
makes no assumption about the effect of moving up from the
home position.
Area clears
If the terminal can clear from the current position to the
end of the line, leaving the cursor where it is, this should
be given as ce. If the terminal can clear from the current
position to the end of the display, then this should be
given as cd. The editor only uses cd from the first column
of a line.
Insert/delete line
If the terminal can open a new blank line before the line
where the cursor is, this should be given as al; this is
done only from the first position of a line. The cursor
must then appear on the newly blank line. If the terminal
can delete the line which the cursor is on, then this should
be given as dl; this is done only from the first position on
the line to be deleted. If the terminal can scroll the
screen backwards, then this can be given as sb, but just al
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suffices. If the terminal can retain display memory above
then the da capability should be given; if display memory
can be retained below then db should be given. These let
the editor understand that deleting a line on the screen may
bring non-blank lines up from below or that scrolling back
with sb may bring down non-blank lines.
Insert/delete character
There are two basic kinds of intelligent terminals with
respect to insert/delete character which can be described
using termcap. The most common insert/delete character
operations affect only the characters on the current line
and shift characters off the end of the line rigidly. Other
terminals, such as the Concept 100 and the Perkin Elmer Owl,
make a distinction between typed and untyped blanks on the
screen, shifting upon an insert or delete only to an untyped
blank on the screen which is either eliminated, or expanded
to two untyped blanks. You can find out which kind of
terminal you have by clearing the screen and then typing
text separated by cursor motions. Type ``abc def'' using
local cursor motions (not spaces) between the ``abc'' and
the ``def''. Then position the cursor before the ``abc''
and put the terminal in insert mode. If typing characters
causes the rest of the line to shift rigidly and characters
to fall off the end, then your terminal does not distinguish
between blanks and untyped positions. If the ``abc'' shifts
over to the ``def'' which then move together around the end
of the current line and onto the next as you insert, you
have the second type of terminal, and should give the
capability in, which stands for ``insert null''. If your
terminal does something different and unusual then you may
have to modify the editor to get it to use the insert mode
your terminal defines. We have seen no terminals which have
an insert mode not falling into one of these two classes.
The editor can handle both terminals which have an insert
mode, and terminals which send a simple sequence to open a
blank position on the current line. Give as im the sequence
to get into insert mode, or give it an empty value if your
terminal uses a sequence to insert a blank position. Give
as ei the sequence to leave insert mode (give this, with an
empty value also if you gave im so). Now give as ic any
sequence needed to be sent just before sending the character
to be inserted. Most terminals with a true insert mode will
not give ic, terminals which send a sequence to open a
screen position should give it here. (Insert mode is
preferable to the sequence to open a position on the screen
if your terminal has both.) If post insert padding is
needed, give this as a number of milliseconds in ip (a
string option). Any other sequence which may need to be
sent after an insert of a single character may also be given
in ip.
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It is occasionally necessary to move around while in insert
mode to delete characters on the same line (e.g. if there is
a tab after the insertion position). If your terminal
allows motion while in insert mode you can give the
capability mi to speed up inserting in this case. Omitting
mi will affect only speed. Some terminals (notably
Datamedia's) must not have mi because of the way their
insert mode works.
Finally, you can specify delete mode by giving dm and ed to
enter and exit delete mode, and dc to delete a single
character while in delete mode.
Highlighting, underlining, and visible bells
If your terminal has sequences to enter and exit standout
mode, these can be given as so and se, respectively. If
there are several flavors of standout mode (such as inverse
video, blinking, or underlining - half bright is not usually
an acceptable standout mode unless the terminal is in
inverse video mode constantly) the preferred mode is inverse
video by itself. If the code to change into or out of
standout mode leaves one or even two blank spaces on the
screen, as the TVI 912 and Teleray 1061 do, then ug should
be given to tell how many spaces are left.
Codes to begin underlining and end underlining can be given
as us and ue respectively. If the terminal has a code to
underline the current character and move the cursor one
space to the right, such as the Microterm Mime, this can be
given as uc. (If the underline code does not move the
cursor to the right, give the code followed by a
nondestructive space.)
Many terminals, such as the HP 2621, automatically leave
standout mode when they move to a new line or the cursor is
addressed. Programs using standout mode should exit
standout mode before moving the cursor or sending a newline.
If the terminal has a way of flashing the screen to indicate
an error quietly (a bell replacement) then this can be given
as vb; it must not move the cursor. If the terminal should
be placed in a different mode during open and visual modes
of ex, this can be given as vs and ve, sent at the start and
end of these modes respectively. These can be used to
change, e.g., from a underline to a block cursor and back.
If the terminal needs to be in a special mode when running a
program that addresses the cursor, the codes to enter and
exit this mode can be given as ti and te. This arises, for
example, from terminals like the Concept with more than one
page of memory. If the terminal has only memory relative
cursor addressing and not screen relative cursor addressing,
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a one screen-sized window must be fixed into the terminal
for cursor addressing to work properly.
If your terminal correctly generates underlined characters
(with no special codes needed) even though it does not
overstrike, then you should give the capability ul. If
overstrikes are erasable with a blank, then this should be
indicated by giving eo.
Keypad
If the terminal has a keypad that transmits codes when the
keys are pressed, this information can be given. Note that
it is not possible to handle terminals where the keypad only
works in local (this applies, for example, to the unshifted
HP 2621 keys). If the keypad can be set to transmit or not
transmit, give these codes as ks and ke. Otherwise the
keypad is assumed to always transmit. The codes sent by the
left arrow, right arrow, up arrow, down arrow, and home keys
can be given as kl, kr, ku, kd, and kh respectively. If
there are function keys such as f0, f1, ..., f9, the codes
they send can be given as k0, k1, ..., k9. If these keys
have labels other than the default f0 through f9, the labels
can be given as l0, l1, ..., l9. If there are other keys
that transmit the same code as the terminal expects for the
corresponding function, such as clear screen, the termcap 2
letter codes can be given in the ko capability, for example,
``:ko=cl,ll,sf,sb:'', which says that the terminal has
clear, home down, scroll down, and scroll up keys that
transmit the same thing as the cl,ll,sf, and sb entries.
The ma entry is also used to indicate arrow keys on
terminals which have single character arrow keys. It is
obsolete but still in use in version 2 of vi, which must be
run on some minicomputers due to memory limitations. This
field is redundant with kl, kr, ku, kd, and kh. It consists
of groups of two characters. In each group, the first
character is what an arrow key sends, the second character
is the corresponding vi command. These commands are h for
kl, j for kd, k for ku, l for kr, and H for kh. For
example, the mime would be :ma=CONTROL-Kj^Zk^Xl: indicating
arrow keys left (CONTROL-h), down (CONTROL-k), up (CONTROL-
z), and right (CONTROL-x). (There is no home key on the
mime.)
Miscellaneous
If the terminal requires other than a null (zero) character
as a pad, then this can be given as pc.
If tabs on the terminal require padding, or if the terminal
uses a character other than CONTROL-i to tab, then this can
be given as ta.
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Hazeltine terminals, which don't allow `~' characters to be
printed should indicate hz. Datamedia terminals, which echo
carriage-return linefeed for carriage return and then ignore
a following linefeed should indicate nc. Early Concept
terminals, which ignore a linefeed immediately after an am
wrap, should indicate xn. If an erase-eol is required to
get rid of standout (instead of merely writing on top of
it), xs should be given. Teleray terminals, where tabs turn
all characters moved over to blanks, should indicate xt.
Other specific terminal problems may be corrected by adding
more capabilities of the form xx.
Other capabilities include is, an initialization string for
the terminal, and if, the name of a file containing long
initialization strings. These strings are expected to
properly clear and then set the tabs on the terminal, if the
terminal has settable tabs. If both are given, is will be
printed before if. This is useful where if is
/usr/lib/tabset/std but is clears the tabs first.
Similar Terminals
If there are two very similar terminals, one can be defined
as being just like the other with certain exceptions. The
string capability tc can be given with the name of the
similar terminal. This capability must be last and the
combined length of the two entries must not exceed 1024.
Since termlib routines search the entry from left to right,
and since the tc capability is replaced by the corresponding
entry, the capabilities given at the left override the ones
in the similar terminal. A capability can be cancelled with
xx@ where xx is the capability. For example, the entry:
hn|2621nl:ks@:ke@:tc=2621:
defines a ``2621nl'' that does not have the ks or ke
capabilities, and hence does not turn on the function key
labels when in visual mode. This is useful for different
modes for a terminal, or for different user preferences.
FILES
/etc/termcap file containing terminal descriptions
SEE ALSO
ex(1), tset(1), ul(1), vi(1), termcap(3X).
BUGS
ex allows only 256 characters for string capabilities, and
the routines in termcap(3X) do not check for overflow of
this buffer. The total length of a single entry (excluding
only escaped newlines) may not exceed 1024.
The ma, vs, and ve entries are specific to the vi program.
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Not all programs support all entries. There are entries
that are not supported by any program.
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