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Once you know the capabilities of your terminal, you have to describe them in your terminal description. You describe them with a string of comma-separated fields that contain the abbreviated terminfo name and, in some cases, the terminal's value for each capability. For example, bel is the abbreviated name for the beeping or ringing capability. On most terminals, a <CTRL-G> is the instruction that produces a beeping sound. Therefore, the beeping capability would be shown in the terminal description as bel=^G,.
The list of capabilities may continue onto multiple lines as long as white space (that is, tabs and spaces) begins every line but the first of the description. Comments can be included in the description by putting a # at the beginning of the line.
The oldterminfo(4) manual page has a complete list of the capabilities you can use in a terminal description. This list contains the name of the capability, the abbreviated name used in the database, the two-letter code that corresponds to the old termcap database name, and a short description of the capability. The abbreviated name that you will use in your database descriptions is shown in the column titled ``Capname.''
A terminal's character sequence (value)
for a capability can be a keyed operation (like <CTRL-G>),
a numeric value, or a parameter string containing the sequence
of operations required to achieve the particular capability.
In a terminal description,
certain characters are used after the capability
name to show what type of character sequence is required.
Explanations of these characters follow:
Sometimes, it may be necessary to comment out a capability so that the terminal ignores this particular field. This is done by placing a period ( . ) in front of the abbreviated name for the capability. For example, if you would like to comment out the beeping capability, the description entry would appear as
.bel=^G,With this background information about specifying capabilities, let us add the capability string to our description of myterm. We will consider basic, screen-oriented, keyboard-entered, and parameter string capabilities.
Some capabilities common to most terminals are bells, columns, lines on the screen, and overstriking of characters, if necessary. Suppose our fictitious terminal has these and a few other capabilities, as listed below. Note that the list gives the abbreviated terminfo name for each capability in the parentheses following the capability description:
myterm|mytm|mine|fancy|terminal|My FANCY terminal, am, bel=^G, cols#80, lines#30, xon,
Screen-oriented capabilities manipulate the contents of a screen. Our example terminal myterm has the following screen-oriented capabilities. Again, the abbreviated command associated with the given capability is shown in parentheses.
myterm|mytm|mine|fancy|terminal|My FANCY Terminal, am, bel=^G, cols#80, lines#30, xon, cr=^M, cuu1=^K, cud1=^J, cub1=^H, cuf1=^L, smso=\ED, rmso=\EZ, el=\EK$<3>, ind=\n,
Keyboard-entered capabilities are sequences generated when a key is typed on a terminal keyboard. Most terminals have, at least, a few special keys on their keyboard, such as arrow keys and the backspace key. Our example terminal has several of these keys whose sequences are, as follows:
myterm|mytm|mine|fancy|terminal|My FANCY Terminal, am, bel=^G, cols#80, lines#30, xon, cr=^M, cuu1=^K, cud1=^J, cub1=^H, cuf1=^L, smso=\ED, rmso=\EZ, el=\EK$<3>, ind=, kbs=^H, kcuu1=\E[A, kcud1=\E[B, kcuf1=\E[C, kcub1=\E[D, khome=\E[H,
Parameter string capabilities are capabilities that can take parameters -- for example, those used to position a cursor on a screen or turn on a combination of video modes. To address a cursor, the cup capability is used and is passed two parameters: the row and column to address. String capabilities, such as cup and set attributes (sgr) capabilities, are passed arguments in a terminfo program by the tparm routine.
The arguments to string capabilities are manipulated with special '%' sequences similar to those found in a printf [see fprintf(3S)] statement. In addition, many of the features found on a simple stack-based RPN calculator are available. cup, as noted above, takes two arguments: the row and column. sgr, takes nine arguments, one for each of the nine video attributes. See oldterminfo(4) for the list and order of the attributes and further examples of sgr.
Our fancy terminal's cursor position sequence requires a row and column to be output as numbers separated by a semicolon, preceded by <ESCAPE->[ and followed with H. The coordinate numbers are 1-based rather than 0-based. Thus, to move to row 5, column 18, from (0,0), the sequence 'ESCAPE-[ 6 ; 19 H' would be output.
Integer arguments are pushed onto the stack with a '%p' sequence followed by the argument number, such as '%p2' to push the second argument. A shorthand sequence to increment the first two arguments is '%i'. To output the top number on the stack as a decimal, a '%d' sequence is used, exactly as in printf.
Our terminal's cup sequence is:
cup=\E[%i%p1%d;%p2%dH,which is built from the following elements:
| \E[ | Output <ESC-[> |
| %i | Increment the two arguments |
| %p1 | Push the first argument (the row) onto the stack |
| %d | Output the row as a decimal |
| ; | Output a semi-colon |
| %p2 | Push the second argument (the column) onto the stack |
| %d | Output the column as a decimal |
| H | Output the trailing letter |
Adding this new information to our database entry for myterm produces:
myterm|mytm|mine|fancy|terminal|My FANCY Terminal, am, bel=^G, cols#80, lines#30, xon, cr=^M, cuu1=^K, cud1=^J, cub1=^H, cuf1=^L, smso=\ED, rmso=\EZ, el=\EK$<3>, ind=, kbs=^H, kcuu1=\E[A, kcud1=\E[B, kcuf1=\E[C, kcub1=\E[D, khome=\E[H, cup=\E[%i%p1%d;%p2%dH,See oldterminfo(4) for more information about parameter string capabilities.