terminal capability database
termcap file is a database describing
terminals, used, for example, by vi(1) and curses(3). Terminals are described in
termcap by giving a set of capabilities that they
have and by describing how operations are performed. Padding requirements
and initialization sequences are included in
termcap consist of a number of
`:'-separated fields. The first entry for each terminal gives the names that
are known for the terminal, separated by `|' characters. The first name
given is the most common abbreviation for the terminal. The last name given
should be a long name fully identifying the terminal, and all others are
understood as synonyms for the terminal name. All names but the last should
be in lower case and contain no blanks; the last name may well contain upper
case characters and blanks for readability.
Terminal names (except for the last, verbose entry) should be chosen using the following conventions. The particular piece of hardware making up the terminal should have a root name chosen, thus “hp2621” This name should not contain hyphens. Modes that the hardware can be in or user preferences should be indicated by appending a hyphen and an indicator of the mode. Therefore, a “vt100” in 132-column mode would be “vt100-w”.
The following suffixes should be used where possible:
|-w||Wide mode (more than 80 columns).||vt100-w|
|-am||With automatic margins (usually default).||vt100-am|
|-nam||Without automatic margins.||vt100-nam|
|-n||Number of lines on screen.||aaa-60|
|-na||arrow keys (leave them in local).||concept100-na|
|-np||Number of pages of memory.||concept100-4p|
The characters in the Notes function field in the table have the following meanings (more than one may apply to a capability):
N Indicates numeric parameter(s). P Indicates that padding may be specified. * Indicates that padding may be based on the number of lines affected. o Indicates capability is obsolete.
“Obsolete” capabilities have no terminfo(5) equivalents, since they were considered useless, or are subsumed by other capabilities. New software should not rely on them at all.
|ae||str||(P)||End alternate character set.|
|AL||str||(NP*)||Add n new blank lines|
|al||str||(P*)||Add new blank line.|
|am||bool||Terminal has automatic margins.|
|as||str||(P)||Start alternate character set.|
|bc||str||(o)||Backspace if not ^H.|
|bl||str||(P)||Audible signal (bell).|
|bs||bool||(o)||Terminal can backspace with ^H.|
|bw||bool||le (backspace) wraps from column 0 to last column.|
|CC||str||Terminal settable command character in prototype.|
|cd||str||(P*)||Clear to end of display.|
|ce||str||(P)||Clear to end of line.|
|ch||str||(NP)||Set cursor column (horizontal position).|
|cl||str||(P*)||Clear screen and home cursor.|
|CM||str||(NP)||Memory-relative cursor addressing.|
|cm||str||(NP)||Screen-relative cursor motion.|
|co||num||Number of columns in a line (see BUGS section below).|
|cs||str||(NP)||Change scrolling region (VT100).|
|ct||str||(P)||Clear all tab stops.|
|cv||str||(NP)||Set cursor row (vertical position).|
|da||bool||Display may be retained above the screen.|
|dB||num||(o)||Milliseconds bs delay needed (default 0).|
|db||bool||Display may be retained below the screen.|
|DC||str||(NP*)||Delete n characters.|
|dC||num||(o)||Milliseconds cr delay needed (default 0).|
|dF||num||(o)||Milliseconds ff delay needed (default 0).|
|DL||str||(NP*)||Delete n lines.|
|dm||str||Enter delete mode.|
|dN||num||(o)||Milliseconds nl delay needed (default 0).|
|DO||str||(NP*)||Move cursor down n lines.|
|do||str||Down one line.|
|ds||str||Disable status line.|
|dT||num||(o)||Milliseconds of horizontal tab delay needed (default 0).|
|dV||num||(o)||Milliseconds of vertical tab delay needed (default 0).|
|ec||str||(NP)||Erase n characters.|
|ed||str||End delete mode.|
|ei||str||End insert mode.|
|eo||bool||Can erase overstrikes with a blank.|
|es||bool||Escape can be used on the status line.|
|ff||str||(P*)||Hardcopy terminal page eject.|
|fs||str||Return from status line.|
|gn||bool||Generic line type, for example dialup, switch).|
|hd||str||Half-line down (forward 1/2 linefeed).|
|hs||bool||Has extra “status line”.|
|hu||str||Half-line up (reverse 1/2 linefeed).|
|hz||bool||Cannot print ``~'' (Hazeltine).|
|i1-i3||str||Terminal initialization strings (terminfo(5) only)|
|IC||str||(NP*)||Insert n blank characters.|
|if||str||Name of file containing initialization string.|
|im||str||Enter insert mode.|
|in||bool||Insert mode distinguishes nulls.|
|iP||str||Pathname of program for initialization (terminfo(5) only)|
|ip||str||(P*)||Insert pad after character inserted.|
|is||str||Terminal initialization string (
|it||num||Tabs initially every n positions.|
|K1||str||Sent by keypad upper left.|
|K2||str||Sent by keypad center.|
|K3||str||Sent by keypad upper right.|
|K4||str||Sent by keypad lower left.|
|K5||str||Sent by keypad lower right.|
|k0-k9||str||Sent by function keys 0-9.|
|kA||str||Sent by insert-line key.|
|ka||str||Sent by clear-all-tabs key.|
|kb||str||Sent by backspace key.|
|kC||str||Sent by clear-screen or erase key.|
|kD||str||Sent by delete-character key.|
|kd||str||Sent by down-arrow key.|
|kE||str||Sent by clear-to-end-of-line key.|
|ke||str||Out of “keypad transmit” mode.|
|kF||str||Sent by scroll-forward/down key.|
|kH||str||Sent by home-down key.|
|kh||str||Sent by home key.|
|kI||str||Sent by insert-character or enter-insert-mode key.|
|kL||str||Sent by delete-line key.|
|kl||str||Sent by left-arrow key.|
|kM||str||Sent by insert key while in insert mode.|
|km||bool||Has a “meta” key (shift, sets parity bit).|
|kN||str||Sent by next-page key.|
|kn||num||(o)||Number of function (k0-k9) keys (default 0).|
|ko||str||(o)||Termcap entries for other non-function keys.|
|kP||str||Sent by previous-page key.|
|kR||str||Sent by scroll-backward/up key.|
|kr||str||Sent by right-arrow key.|
|kS||str||Sent by clear-to-end-of-screen key.|
|ks||str||Put terminal in “keypad transmit” mode.|
|kT||str||Sent by set-tab key.|
|kt||str||Sent by clear-tab key.|
|ku||str||Sent by up-arrow key.|
|l0-l9||str||Labels on function keys if not “fn”.|
|LE||str||(NP)||Move cursor left n positions.|
|le||str||(P)||Move cursor left one position.|
|li||num||Number of lines on screen or page (see BUGS section below).|
|ll||str||Last line, first column.|
|lm||num||Lines of memory if > li (0 means varies).|
|ma||str||(o)||Arrow key map (used by vi(1) version 2 only).|
|mb||str||Turn on blinking attribute.|
|md||str||Turn on bold (extra bright) attribute.|
|me||str||Turn off all attributes.|
|mh||str||Turn on half-bright attribute.|
|mi||bool||Safe to move while in insert mode.|
|mk||str||Turn on blank attribute (characters invisible).|
|ml||str||(o)||Memory lock on above cursor.|
|mm||str||Turn on “meta mode” (8th bit).|
|mo||str||Turn off “meta mode”.|
|mp||str||Turn on protected attribute.|
|mr||str||Turn on reverse-video attribute.|
|ms||bool||Safe to move in standout modes.|
|mu||str||(o)||Memory unlock (turn off memory lock).|
|nc||bool||(o)||No correctly-working cr (Datamedia 2500, Hazeltine 2000).|
|nd||str||Non-destructive space (cursor right).|
|NL||bool||(o)"||\n is newline, not line feed.|
|nl||str||(o)||Newline character if not \n.|
|ns||bool||(o)||Terminal doesn't scroll.|
|nw||str||(P)||Newline (behaves like cr followed by do).|
|pb||num||Lowest baud where delays are required.|
|pc||str||Pad character (default NUL).|
|pf||str||Turn off the printer.|
|pk||str||Program function key n to type string s (terminfo(5) only)|
|pl||str||Program function key n to execute string s (terminfo(5) only)|
|pO||str||(N)||Turn on the printer for n bytes.|
|po||str||Turn on the printer.|
|ps||str||Print contents of the screen.|
|pt||bool||(o)||Has hardware tabs (may need to be set with is).|
|px||str||Program function key n to transmit string s (terminfo(5) only)|
|r1-r3||str||Reset terminal completely to sane modes (terminfo(5) only)|
|rc||str||(P)||Restore cursor to position of last sc.|
|rf||str||Name of file containing reset codes.|
|RI||str||(NP)||Move cursor right n positions.|
|rp||str||(NP*)||Repeat character c n times.|
|rs||str||Reset terminal completely to sane modes (
|sa||str||(NP)||Define the video attributes.|
|sc||str||(P)||Save cursor position.|
|se||str||End standout mode.|
|SF||str||(NP*)||Scroll forward n lines.|
|sf||str||(P)||Scroll text up.|
|sg||num||Number of garbage chars left by so or se (default 0).|
|so||str||Begin standout mode.|
|SR||str||(NP*)||Scroll backward n lines.|
|sr||str||(P)||Scroll text down.|
|st||str||Set a tab in all rows, current column.|
|ta||str||(P)||Tab to next 8-position hardware tab stop.|
|tc||str||Entry of similar terminal; must be last.|
|te||str||String to end programs that use
|ti||str||String to begin programs that use
|ts||str||(N)||Go to status line, column n.|
|uc||str||Underscore one character and move past it.|
|ue||str||End underscore mode.|
|ug||num||Number of garbage chars left by us or ue (default 0).|
|ul||bool||Underline character overstrikes.|
|UP||str||(NP*)||Move cursor up n lines.|
|up||str||Upline (cursor up).|
|us||str||Start underscore mode.|
|vb||str||Visible bell (must not move cursor).|
|ve||str||Make cursor appear normal (undo vs/vi).|
|vi||str||Make cursor invisible.|
|vs||str||Make cursor very visible.|
|vt||num||Virtual terminal number (not supported on all systems).|
|wi||str||(N)||Set current window.|
|ws||num||Number of columns in status line.|
|xn||bool||Newline ignored after 80 columns (Concept).|
|xo||bool||Terminal uses xoff/xon
|xr||bool||(o)||Return acts like ce cr nl (Delta Data).|
|xs||bool||Standout not erased by overwriting (Hewlett-Packard).|
|xt||bool||Tabs ruin, magic so char (Teleray 1061).|
|xx||bool||(o)||Tektronix 4025 insert-line.|
A Sample Entry
The following entry, which describes the Concept-100, is among the
more complex entries in the
termcap file as of this
ca|concept100|c100|concept|c104|concept100-4p|HDS Concept-100:\ :al=3*\E^R:am:bl=^G:cd=16*\E^C:ce=16\E^U:cl=2*^L:cm=\Ea%+ %+ :\ :co#80:.cr=9^M:db:dc=16\E^A:dl=3*\E^B:do=^J:ei=\E\200:eo:im=\E^P:in:\ :ip=16*:is=\EU\Ef\E7\E5\E8\El\ENH\EK\E\200\Eo&\200\Eo\47\E:k1=\E5:\ :k2=\E6:k3=\E7:kb=^h:kd=\E<:ke=\Ex:kh=\E?:kl=\E>:kr=\E=:ks=\EX:\ :ku=\E;:le=^H:li#24:mb=\EC:me=\EN\200:mh=\EE:mi:mk=\EH:mp=\EI:\ :mr=\ED:nd=\E=:pb#9600:rp=0.2*\Er%.%+ :se=\Ed\Ee:sf=^J:so=\EE\ED:\ :.ta=8\t:te=\Ev \200\200\200\200\200\200\Ep\r\n:\ :ti=\EU\Ev 8p\Ep\r:ue=\Eg:ul:up=\E;:us=\EG:\ :vb=\Ek\200\200\200\200\200\200\200\200\200\200\200\200\200\200\EK:\ :ve=\Ew:vs=\EW:vt#8:xn:\ :bs:cr=^M:dC#9:dT#8:nl=^J:ta=^I:pt:
Entries may continue onto multiple lines by giving a
\’ as the last character of a line,
and empty fields may be included for readability (here between the last
field on a line and the first field on the next). Comments may be included
on lines beginning with ‘
Types of Capabilities
termcap are of three
types: Boolean capabilities, which indicate particular features that the
terminal has; numeric capabilities, giving the size of the display or the
size of other attributes; and string capabilities, which give character
sequences that can be used to perform particular terminal operations. All
capabilities have two-letter codes. For instance, the fact that the Concept
margins (an automatic return and linefeed when the end of a line is
reached) is indicated by the Boolean capability am. Hence
the description of the Concept includes am.
Boolean capabilities are defined by their name, fo. They have no argument. The presence of a boolean capability name sets its value to true. A capability value will be reverted to false, by appending a @ char after the name, such as fo@.
Numeric capabilities are followed by the character `#' then the value. In the example above co, which indicates the number of columns the display 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-letter code, an `=', then a string ending at the next following `:'. A delay in milliseconds may appear after the `=' in such a capability, which causes padding characters to be supplied by tputs(3) after the remainder of the string is sent to provide this delay. The delay can be either a number, such as `20', or a number followed by an `*', such as `3*'. An `*' indicates that the padding required is proportional to the number of lines affected by the operation, and the amount given is the per-affected-line padding required. (In the case of insert-character, the factor is still the number of lines affected; this is always 1 unless the terminal has in and the software uses it.) When an `*' is specified, it is sometimes useful to give a delay of the form `3.5' to specify a delay per line to tenths of milliseconds. (Only one decimal place is allowed.)
A number of escape sequences are provided in the
string-valued capabilities for easy encoding of control characters there.
\E maps to an
^X maps to a control-X
for any appropriate X, and the sequences \n
\r \t \b
\f map to linefeed, return, tab, backspace, and formfeed,
respectively. Finally, characters may be given as three octal digits after a
\, and the characters
\ 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
NUL character in a string
capability, it must be encoded as \200. (The routines that
termcap use C strings and strip the high
bits of the output very late, so that a \200 comes out as
a \000 would.)
Sometimes individual capabilities must be commented out. To do this, put a period before the capability name. For example, see the first cr and ta in the example above.
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 vi(1) 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
vi(1). To easily
test a new terminal description you are working on you can put it in your
home directory in a file called .termcap and
programs will look there before looking in
/usr/share/misc/termcap. You can also set the
TERMPATH to a list of absolute
file pathnames (separated by spaces or colons), one of which contains the
description you are working on, and programs will search them in the order
listed, and nowhere else. See
TERMCAP environment variable
is usually set to the
termcap entry itself to avoid
reading files when starting up a program.
To get the padding for insert-line right (if the terminal manufacturer did not document it), a severe test is to use vi(1) to edit /etc/passwd at 9600 baud, delete roughly 16 lines from the middle of the screen, then hit the `u' key several times quickly. If the display messes up, more padding is usually needed. A similar test can be used for insert-character.
The number of columns on each line of the display is given by the co numeric capability. If the display is a terminal, then the number of lines on the screen is given by the li capability. If the display wraps around to the beginning of the next line when the cursor reaches the right margin, then it should have the am capability. If the terminal can clear its screen, the code to do this is given by the cl string capability. If the terminal overstrikes (rather than clearing the position when a character is overwritten), it should have the os capability. If the terminal is a printing terminal, with no soft copy unit, give it both hc and os. (os applies to storage scope terminals, such as the Tektronix 4010 series, as well as to hard copy and APL terminals.) If there is a code to move the cursor to the left edge of the current row, give this as cr. (Normally this will be carriage-return, ^M.) If there is a code to produce an audible signal (bell, beep, etc.), give this as bl.
If there is a code (such as backspace) to move the cursor one position to the left, that capability should be given as le. Similarly, codes to move to the right, up, and down should be given as nd, up, and do, respectively. These local cursor motions should not alter the text they pass over; for example, you would not normally use “nd= ” unless the terminal has the os capability, because the space would erase the character moved over.
A very important point here is that the local cursor motions
termcap have undefined behavior at the
left and top edges of a terminal. Programs should never attempt to backspace
around the left edge, unless bw is given, and never
attempt to go up off the top using local cursor motions.
In order to scroll text up, a program goes to the bottom left corner of the screen and sends the sf (index) string. To scroll text down, a program goes to the top left corner of the screen and sends the sr (reverse index) string. The strings sf and sr have undefined behavior when not on their respective corners of the screen. Parameterized versions of the scrolling sequences are SF and SR, which have the same semantics as sf and sr except that they take one parameter and scroll that many lines. They also have undefined behavior except at the appropriate corner of the screen.
The am capability tells whether the cursor
sticks at the right edge of the screen when text is output there, but this
does not necessarily apply to nd from the last column.
Leftward local motion is defined from the left edge only when
bw is given; then an le from the left
edge will move to the right edge of the previous row. This is useful for
drawing a box around the edge of the screen, for example. If the terminal
has switch-selectable automatic margins, the
description usually assumes that this feature is on, i.e.
am. If the terminal has a command that moves to the first
column of the next line, that command can be given as nw
(newline). It is permissible for this to clear the remainder of the current
line, so if the terminal has no correctly working CR and LF it may still be
possible to craft a working nw out of one or both of
These capabilities suffice to describe hardcopy and “glass-tty” terminals. Thus the Teletype model 33 is described as
T3|tty33|33|tty|Teletype model 33:\ :bl=^G:co#72:cr=^M:do=^J:hc:os:
and the Lear Siegler ADM-3 is described as
l3|adm3|3|LSI ADM-3:\ :am:bl=^G:cl=^Z:co#80:cr=^M:do=^J:le=^H:li#24:sf=^J:
Cursor addressing and other strings requiring parameters are described by a parameterized string capability, with printf(3)-like escapes %x in it, while other characters are passed through unchanged. For example, to address the cursor the cm capability is given, using two parameters: the row and column to move to. (Rows and columns are numbered from zero and refer to the physical screen visible to the user, not to any unseen memory. If the terminal has memory-relative cursor addressing, that can be indicated by an analogous CM capability.)
The % encodings have the following meanings:
- output `%'
- output value as in printf(3) %d
- output value as in printf(3) %2d
- output value as in printf(3) %3d
- output value as in printf(3) %c
- add x to value, then do %.
- if value > x then add y, no output
- reverse order of two parameters, no output
- increment by one, no output
- exclusive-or all parameters with 0140 (Datamedia 2500)
- BCD (16*(value/10)) + (value%10), no output
- Reverse coding (value - 2*(value%16)), no output (Delta Data)
Consider the Hewlett-Packard 2645, 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 row and column coordinates is
reversed here and that the row and column are sent as two-digit integers.
Thus its cm capability is
The Datamedia 2500 needs the current row and column sent
encoded in binary using “%.”. Terminals that use
“%.” need to be able to backspace the cursor
(le) and to move the cursor up one line on the screen
(up). This is necessary because it is not always safe to
\r, as the system may change or discard them. (Programs
termcap must set terminal modes so that tabs
are not expanded, so \t is safe to send. This turns out to
be essential for the Ann Arbor 4080.)
A final example is the Lear Siegler ADM-3a, which offsets row and
column by a blank character, thus “
Row or column absolute cursor addressing can be given as single parameter capabilities ch (horizontal position absolute) and cv (vertical position absolute). Sometimes these are shorter than the more general two-parameter sequence (as with the Hewlett-Packard 2645) and can be used in preference to cm. If there are parameterized local motions (e.g., move n positions to the right) these can be given as DO, LE, RI, and UP with a single parameter indicating how many positions to move. These are primarily useful if the terminal does not have cm, such as the Tektronix 4025.
If the terminal has a fast way to home the cursor (to the very upper left corner of the screen), 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 a program should never do this itself (unless ll does), because it can make no assumption about the effect of moving up from the home position. Note that the home position is the same as cursor address (0,0): to the top left corner of the screen, not of memory. (Therefore, the “\EH” sequence on Hewlett-Packard terminals cannot be used for ho.)
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, this should be given as cd. cd must only be invoked from the first column of a line. (Therefore, it can be simulated by a request to delete a large number of lines, if a true cd is not available.)
If the terminal can open a new blank line before the line containing the cursor, this should be given as al; this must be invoked only from the first position of a line. The cursor must then appear at the left of the newly blank line. If the terminal can delete the line that the cursor is on, this should be given as dl; this must only be used from the first position on the line to be deleted. Versions of al and dl which take a single parameter and insert or delete that many lines can be given as AL and DL. If the terminal has a settable scrolling region (like the VT100), the command to set this can be described with the cs capability, which takes two parameters: the top and bottom lines of the scrolling region. The cursor position is, alas, undefined after using this command. It is possible to get the effect of insert or delete line using this command — the sc and rc (save and restore cursor) commands are also useful. Inserting lines at the top or bottom of the screen can also be done using sr or sf on many terminals without a true insert/delete line, and is often faster even on terminals with those features.
If the terminal has the ability to define a window as part
of memory which all commands affect, it should be given as the parameterized
string wi. The four
parameters are the starting and ending lines in memory and the starting and
ending columns in memory, in that order. (This
terminfo(5) capability is described for completeness. It is unlikely
termcap-using program will support it.)
If the terminal can retain display memory above the screen, then the da capability should be given; if display memory can be retained below, then db should be given. These indicate that deleting a line or scrolling may bring non-blank lines up from below or that scrolling back with sr may bring down non-blank lines.
There are two basic kinds of intelligent terminals with respect to
insert/delete character that 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 determine the kind of terminal you have by clearing
the screen then typing text separated by cursor motions. Type
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, then you have the second type of
terminal and should give the capability in, which stands
for “insert null”. While these are two logically separate
attributes (one line vs. multi-line insert mode, and
special treatment of untyped spaces), we have seen no terminals whose insert
mode cannot be described with the single attribute.
termcap can describe both
terminals that have an insert mode and terminals that send a simple sequence
to open a blank position on the current line. Give as im
the sequence to get into insert mode. Give as ei the
sequence to leave insert mode. Now give as ic any sequence
that needs to be sent just before each character to be inserted. Most
terminals with a true insert mode will not give ic;
terminals that use a sequence to open a screen position should give it here.
(If your terminal has both, insert mode is usually preferable to
ic. Do not give both unless the terminal actually requires
both to be used in combination.) If post-insert padding is needed, give this
as a number of milliseconds in ip (a string option). Any
other sequence that may need to be sent after insertion of a single
character can also be given in ip. If your terminal needs
to be placed into an `insert mode' and needs a special code preceding each
inserted character, then both im/ ei and
ic can be given, and both will be used. The
IC capability, with
one parameter n, will repeat the effects of
ic n times.
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 dc to delete a single character, DC with one parameter n to delete n characters, and delete mode by giving dm and ed to enter and exit delete mode (which is any mode the terminal needs to be placed in for dc to work).
Highlighting, Underlining, and Visible Bells
If your terminal has one or more kinds of display attributes, these can be represented in a number of different ways. You should choose one display form as standout mode, representing a good high-contrast, easy-on-the-eyes format for highlighting error messages and other attention getters. (If you have a choice, reverse video plus half-bright is good, or reverse video alone.) The sequences to enter and exit standout mode are given as so and se, respectively. If the code to change into or out of standout mode leaves one or even two blank spaces or garbage characters on the screen, as the TVI 912 and Teleray 1061 do, then sg should be given to tell how many characters are left.
Codes to begin underlining and end underlining can be given as us and ue, respectively. Underline mode change garbage is specified by ug, similar to sg. If the terminal has a code to underline the current character and move the cursor one position to the right, such as the Microterm Mime, this can be given as uc.
Other capabilities to enter various highlighting modes include mb (blinking), md (bold or extra bright), mh (dim or half-bright), mk (blanking or invisible text), mp (protected), mr (reverse video), me (turn off all attribute modes), as (enter alternate character set mode), and ae (exit alternate character set mode). Turning on any of these modes singly may or may not turn off other modes.
If there is a sequence to set arbitrary combinations of mode, this
should be given as sa (set attributes), taking 9
parameters. Each parameter is either 0 or 1, as the corresponding attributes
is on or off. The 9 parameters are, in order: standout, underline, reverse,
blink, dim, bold, blank, protect, and alternate character set. Not all modes
need be supported by sa, only those for which
corresponding attribute commands exist. (It is unlikely that a
termcap-using program will support this capability,
which is defined for compatibility with
Terminals with the “magic cookie” glitches (sg and ug), rather than maintaining extra attribute bits for each character cell, instead deposit special “cookies”, or “garbage characters”, when they receive mode-setting sequences, which affect the display algorithm.
Some terminals, such as the Hewlett-Packard 2621, automatically leave standout mode when they move to a new line or when the cursor is addressed. Programs using standout mode should exit standout mode on such terminals before moving the cursor or sending a newline. On terminals where this is not a problem, the ms capability should be present to say that this overhead is unnecessary.
If the terminal has a way of flashing the screen to indicate an error quietly (a bell replacement), this can be given as vb; it must not move the cursor.
If the cursor needs to be made more visible than normal when it is not on the bottom line (to change, for example, a non-blinking underline into an easier-to-find block or blinking underline), give this sequence as vs. If there is a way to make the cursor completely invisible, give that as vi. The capability ve, which undoes the effects of both of these modes, should also be given.
If your terminal correctly displays 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, this should be indicated by giving eo.
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 mode (this applies, for example, to the unshifted Hewlett-Packard 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. The codes transmitted by certain other special keys can be given: kH (home down), kb (backspace), ka (clear all tabs), kt (clear the tab stop in this column), kC (clear screen or erase), kD (delete character), kL (delete line), kM (exit insert mode), kE (clear to end of line), kS (clear to end of screen), kI (insert character or enter insert mode), kA (insert line), kN (next page), kP (previous page), kF (scroll forward/down), kR (scroll backward/up), and kT (set a tab stop in this column). In addition, if the keypad has a 3 by 3 array of keys including the four arrow keys, then the other five keys can be given as K1, K2, K3, K4, and K5. These keys are useful when the effects of a 3 by 3 directional pad are needed. The obsolete ko capability formerly used to describe “other” function keys has been completely supplanted by the above capabilities.
ma entry is also used
to indicate arrow keys on terminals that 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, and 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 have
ma=^Hh^Kj^Zk^Xl” indicating arrow
keys left (^H), down (^K), up (^Z), and right (^X). (There is no home key on
Tabs and Initialization
If the terminal needs to be in a special mode when running a
program that uses these capabilities, the codes to enter and exit this mode
can be given as ti and
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, a screen-sized window must be fixed
into the display for cursor addressing to work properly. This is also used
for the Tektronix 4025, where ti sets the command
character to be the one used by
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 set the terminal into modes consistent with the rest of the
termcap description. They are normally sent to the
terminal by the tset(1) program each time the user logs in. They will be printed in
the following order: is; setting tabs using
ct and st; and finally
(terminfo(5) uses i1-i2 instead of
is and runs the program
iP and prints
i3 after the other initializations.) A pair of sequences
that does a harder reset from a totally unknown state can be analogously
given as rs and if. These strings are
output by the reset(1) program, which is used when the terminal gets into a wedged
state. (terminfo(5) uses
instead of rs.) Commands are normally placed in
rf only if
they produce annoying effects on the screen and are not necessary when
logging in. For example, the command to set the VT100 into 80-column mode
would normally be part of is, but it causes an annoying
glitch of the screen and is not normally needed since the terminal is
usually already in 80-column mode.
If the terminal has hardware tabs, the command to advance
to the next tab stop can be given as ta (usually
“backtab” command which moves leftward to the previous tab
stop can be given as bt. By convention, if the terminal
driver modes indicate that tab stops are being expanded by the computer
rather than being sent to the terminal, programs should not use
ta or bt even if they are present, since
the user may not have the tab stops properly set. If the terminal has
hardware tabs that are initially set every n positions
when the terminal is powered up, then the numeric parameter
it is given,
showing the number of positions between tab stops. This is normally used by
command to determine whether to set the driver mode for hardware tab
expansion, and whether to set the tab stops. If the terminal has tab stops
that can be saved in nonvolatile memory, the
description can assume that they are properly set.
If there are commands to set and clear tab stops, they can be given as ct (clear all tab stops) and st (set a tab stop in the current column of every row). If a more complex sequence is needed to set the tabs than can be described by this, the sequence can be placed in is or if.
Certain capabilities control padding in the terminal driver. These are primarily needed by hardcopy terminals and are used by the tset(1) program to set terminal driver modes appropriately. Delays embedded in the capabilities cr, sf, le, ff, and ta will cause the appropriate delay bits to be set in the terminal driver. If pb (padding baud rate) is given, these values can be ignored at baud rates below the value of pb. For 4.2BSD tset(1), the delays are given as numeric capabilities dC, dN, dB, dF, and dT instead.
If the terminal requires other than a
(zero) character as a pad, this can be given as pc. Only
the first character of the pc string is used.
If the terminal has commands to save and restore the position of the cursor, give them as sc and rc.
If the terminal has an extra “status line” that is not normally used by software, this fact can be indicated. If the status line is viewed as an extra line below the bottom line, then the capability hs should be given. Special strings to go to a position in the status line and to return from the status line can be given as ts and fs. (fs must leave the cursor position in the same place that it was before ts. If necessary, the sc and rc strings can be included in ts and fs to get this effect.) The capability ts takes one parameter, which is the column number of the status line to which the cursor is to be moved. If escape sequences and other special commands such as tab work while in the status line, the flag es can be given. A string that turns off the status line (or otherwise erases its contents) should be given as ds. The status line is normally assumed to be the same width as the rest of the screen, i.e. co. If the status line is a different width (possibly because the terminal does not allow an entire line to be loaded), then its width in columns can be indicated with the numeric parameter ws.
If the terminal can move up or down half a line, this can be indicated with hu (half-line up) and hd (half-line down). This is primarily useful for superscripts and subscripts on hardcopy terminals. If a hardcopy terminal can eject to the next page (form feed), give this as ff (usually ^L).
If there is a command to repeat a given character a given
number of times (to save time transmitting a large number of identical
characters), this can be indicated with the parameterized string
rp. The first
parameter is the character to be repeated and the second is the number of
times to repeat it. (This is a
terminfo(5) feature that is unlikely to be supported by a program
If the terminal has a settable command character, such as the
Tektronix 4025, this can be indicated with CC. A prototype
command character is chosen which is used in all capabilities. This
character is given in the CC capability to identify it.
The following convention is supported on some UNIX
systems: The environment is to be searched for a
variable, and if found, all occurrences of the prototype character are
replaced by the character in the environment variable. This use of the
CC environment variable is a very bad idea, as it
conflicts with make(1).
Terminal descriptions that do not represent a specific kind of known terminal, such as switch, dialup, patch, and network, should include the gn (generic) capability so that programs can complain that they do not know how to talk to the terminal. (This capability does not apply to virtual terminal descriptions for which the escape sequences are known.)
If the terminal uses xoff/xon (DC3/DC1) handshaking for flow control, give xo. Padding information should still be included so that routines can make better decisions about costs, but actual pad characters will not be transmitted.
If the terminal has a “meta key” which acts as a shift key, setting the 8th bit of any character transmitted, then this fact can be indicated with km. Otherwise, software will assume that the 8th bit is parity and it will usually be cleared. If strings exist to turn this “meta mode” on and off, they can be given as mm and mo.
If the terminal has more lines of memory than will fit on the screen at once, the number of lines of memory can be indicated with lm. An explicit value of 0 indicates that the number of lines is not fixed, but that there is still more memory than fits on the screen.
If the terminal is one of those supported by the UNIX system virtual terminal protocol, the terminal number can be given as vt.
Media copy strings which control an auxiliary printer connected to the terminal can be given as ps: print the contents of the screen; pf: turn off the printer; and po: turn on the printer. When the printer is on, all text sent to the terminal will be sent to the printer. It is undefined whether the text is also displayed on the terminal screen when the printer is on. A variation pO takes one parameter and leaves the printer on for as many characters as the value of the parameter, then turns the printer off. The parameter should not exceed 255. All text, including pf, is transparently passed to the printer while pO is in effect.
Strings to program function keys can be given as
pk, pl, and px. Each
of these strings takes two parameters: the function key number to program
(from 0 to 9) and the string to program it with. Function key numbers out of
this range may program undefined keys in a terminal-dependent manner. The
differences among the capabilities are that pk causes
pressing the given key to be the same as the user typing the given string;
pl causes the string to be executed by the terminal in
local mode; and px causes the string to be transmitted to
the computer. Unfortunately, due to lack of a definition for string
terminfo(5) supports these capabilities.
Glitches and Brain-damage
Hazeltine terminals, which do not allow `~' characters to be displayed, should indicate hz.
The nc capability, now obsolete, formerly indicated Datamedia terminals, which echo \r \n for carriage return then ignore a following linefeed.
Terminals that ignore a linefeed immediately after an am wrap, such as the Concept, should indicate xn.
If ce is required to get rid of standout (instead of merely writing normal text on top of it), xs should be given.
Teleray terminals, where tabs turn all characters moved over to blanks, should indicate xt (destructive tabs). This glitch is also taken to mean that it is not possible to position the cursor on top of a “magic cookie”, and that to erase standout mode it is necessary to use delete and insert line.
The Beehive Superbee, which is unable to correctly
ESC or ^C characters,
has xb, indicating
that the “f1” key is used for
“f2” for ^C. (Only certain Superbees have this problem,
depending on the ROM.)
Other specific terminal problems may be corrected by adding more capabilities of the form x x.
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 entries must not exceed 1024. The capabilities given before tc override those in the terminal type invoked by tc. A capability can be cancelled by placing xx@ to the left of the tc invocation, where xx is the capability. For example, the entry
defines a “2621-nl” that does not have the ks or ke capabilities, 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.
- File containing terminal descriptions.
- Hash database file containing terminal descriptions (see cap_mkdb(1)).
cap_mkdb(1), ex(1), more(1), tset(1), ul(1), vi(1), curses(3), printf(3), termcap(3), terminfo(3), terminfo(5), term(7)
termcap file format appeared in
termcap functions were replaced by
terminfo(5) in AT&T System V UNIX
Release 2.0. The transition will be relatively painless if capabilities
flagged as “obsolete” are avoided.
Lines and columns are now stored by the kernel as well as in the termcap entry. Most programs now use the kernel information primarily; the information in this file is used only if the kernel does not have any information.
vi(1) allows only 256 characters for string capabilities, and the routines in termcap(3) do not check for overflow of this buffer. The total length of a single entry (excluding only escaped newlines) may not exceed 1024.
Not all programs support all entries.