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1114 lines
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1114 lines
46 KiB
Text
This is Info file ./termcap.info, produced by Makeinfo-1.55 from the
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input file ./termcap.texi.
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This file documents the termcap library of the GNU system.
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Copyright (C) 1988 Free Software Foundation, Inc.
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Permission is granted to make and distribute verbatim copies of this
|
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manual provided the copyright notice and this permission notice are
|
||
preserved on all copies.
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||
|
||
Permission is granted to copy and distribute modified versions of
|
||
this manual under the conditions for verbatim copying, provided that
|
||
the entire resulting derived work is distributed under the terms of a
|
||
permission notice identical to this one.
|
||
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||
Permission is granted to copy and distribute translations of this
|
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manual into another language, under the above conditions for modified
|
||
versions, except that this permission notice may be stated in a
|
||
translation approved by the Foundation.
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||
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File: termcap.info, Node: Top, Next: Introduction, Prev: (dir), Up: (dir)
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* Menu:
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* Introduction:: What is termcap? Why this manual?
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* Library:: The termcap library functions.
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* Data Base:: What terminal descriptions in `/etc/termcap' look like.
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* Capabilities:: Definitions of the individual terminal capabilities:
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how to write them in descriptions, and how to use
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their values to do display updating.
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* Summary:: Brief table of capability names and their meanings.
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* Var Index:: Index of C functions and variables.
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||
* Cap Index:: Index of termcap capabilities.
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||
* Index:: Concept index.
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||
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-- The Detailed Node Listing --
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The Termcap Library
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||
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* Preparation:: Preparing to use the termcap library.
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* Find:: Finding the description of the terminal being used.
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||
* Interrogate:: Interrogating the description for particular capabilities.
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* Initialize:: Initialization for output using termcap.
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* Padding:: Outputting padding.
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* Parameters:: Encoding parameters such as cursor positions.
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||
|
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Padding
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||
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* Why Pad:: Explanation of padding.
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* Not Enough:: When there is not enough padding.
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* Describe Padding:: The data base says how much padding a terminal needs.
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* Output Padding:: Using `tputs' to output the needed padding.
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||
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Filling In Parameters
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* Encode Parameters:: The language for encoding parameters.
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* Using Parameters:: Outputting a string command with parameters.
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||
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Sending Display Commands with Parameters
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* tparam:: The general case, for GNU termcap only.
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* tgoto:: The special case of cursor motion.
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The Format of the Data Base
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* Format:: Overall format of a terminal description.
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* Capability Format:: Format of capabilities within a description.
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* Naming:: Naming conventions for terminal types.
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* Inheriting:: Inheriting part of a description from
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a related terminal type.
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* Changing:: When changes in the data base take effect.
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||
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Definitions of the Terminal Capabilities
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* Basic:: Basic characteristics.
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* Screen Size:: Screen size, and what happens when it changes.
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* Cursor Motion:: Various ways to move the cursor.
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* Wrapping:: What happens if you write a character in the last column.
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* Scrolling:: Pushing text up and down on the screen.
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* Windows:: Limiting the part of the window that output affects.
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* Clearing:: Erasing one or many lines.
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* Insdel Line:: Making new blank lines in mid-screen; deleting lines.
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* Insdel Char:: Inserting and deleting characters within a line.
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* Standout:: Highlighting some of the text.
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* Underlining:: Underlining some of the text.
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* Cursor Visibility:: Making the cursor more or less easy to spot.
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* Bell:: Attracts user's attention; not localized on the screen.
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* Keypad:: Recognizing when function keys or arrows are typed.
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* Meta Key:: META acts like an extra shift key.
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* Initialization:: Commands used to initialize or reset the terminal.
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* Pad Specs:: Info for the kernel on how much padding is needed.
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* Status Line:: A status line displays "background" information.
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* Half-Line:: Moving by half-lines, for superscripts and subscripts.
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* Printer:: Controlling auxiliary printers of display terminals.
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||
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File: termcap.info, Node: Introduction, Next: Library, Prev: Top, Up: Top
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Introduction
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************
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"Termcap" is a library and data base that enables programs to use
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display terminals in a terminal-independent manner. It originated in
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Berkeley Unix.
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|
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The termcap data base describes the capabilities of hundreds of
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different display terminals in great detail. Some examples of the
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information recorded for a terminal could include how many columns wide
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it is, what string to send to move the cursor to an arbitrary position
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(including how to encode the row and column numbers), how to scroll the
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screen up one or several lines, and how much padding is needed for such
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a scrolling operation.
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||
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The termcap library is provided for easy access this data base in
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programs that want to do terminal-independent character-based display
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output.
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This manual describes the GNU version of the termcap library, which
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has some extensions over the Unix version. All the extensions are
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identified as such, so this manual also tells you how to use the Unix
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termcap.
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||
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The GNU version of the termcap library is available free as source
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code, for use in free programs, and runs on Unix and VMS systems (at
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least). You can find it in the GNU Emacs distribution in the files
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`termcap.c' and `tparam.c'.
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This manual was written for the GNU project, whose goal is to
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develop a complete free operating system upward-compatible with Unix
|
||
for user programs. The project is approximately two thirds complete.
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||
For more information on the GNU project, including the GNU Emacs editor
|
||
and the mostly-portable optimizing C compiler, send one dollar to
|
||
|
||
Free Software Foundation
|
||
675 Mass Ave
|
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Cambridge, MA 02139
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||
|
||
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File: termcap.info, Node: Library, Next: Data Base, Prev: Introduction, Up: Top
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|
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The Termcap Library
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*******************
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||
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The termcap library is the application programmer's interface to the
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termcap data base. It contains functions for the following purposes:
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* Finding the description of the user's terminal type (`tgetent').
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||
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* Interrogating the description for information on various topics
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(`tgetnum', `tgetflag', `tgetstr').
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||
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||
* Computing and performing padding (`tputs').
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||
|
||
* Encoding numeric parameters such as cursor positions into the
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terminal-specific form required for display commands (`tparam',
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||
`tgoto').
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||
|
||
* Menu:
|
||
|
||
* Preparation:: Preparing to use the termcap library.
|
||
* Find:: Finding the description of the terminal being used.
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||
* Interrogate:: Interrogating the description for particular capabilities.
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||
* Initialize:: Initialization for output using termcap.
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||
* Padding:: Outputting padding.
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||
* Parameters:: Encoding parameters such as cursor positions.
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||
|
||
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||
File: termcap.info, Node: Preparation, Next: Find, Up: Library
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||
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Preparing to Use the Termcap Library
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||
====================================
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||
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||
To use the termcap library in a program, you need two kinds of
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||
preparation:
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||
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* The compiler needs declarations of the functions and variables in
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||
the library.
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||
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On GNU systems, it suffices to include the header file `termcap.h'
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||
in each source file that uses these functions and variables.
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||
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||
On Unix systems, there is often no such header file. Then you must
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||
explictly declare the variables as external. You can do likewise
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for the functions, or let them be implicitly declared and cast
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||
their values from type `int' to the appropriate type.
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||
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||
We illustrate the declarations of the individual termcap library
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functions with ANSI C prototypes because they show how to pass the
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arguments. If you are not using the GNU C compiler, you probably
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cannot use function prototypes, so omit the argument types and
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names from your declarations.
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||
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||
* The linker needs to search the library. Usually either
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||
`-ltermcap' or `-ltermlib' as an argument when linking will do
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this.
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||
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||
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||
File: termcap.info, Node: Find, Next: Interrogate, Prev: Preparation, Up: Library
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||
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||
Finding a Terminal Description: `tgetent'
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=========================================
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||
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An application program that is going to use termcap must first look
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up the description of the terminal type in use. This is done by calling
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||
`tgetent', whose declaration in ANSI Standard C looks like:
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||
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int tgetent (char *BUFFER, char *TERMTYPE);
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||
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||
This function finds the description and remembers it internally so that
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||
you can interrogate it about specific terminal capabilities (*note
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||
Interrogate::.).
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||
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||
The argument TERMTYPE is a string which is the name for the type of
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||
terminal to look up. Usually you would obtain this from the environment
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||
variable `TERM' using `getenv ("TERM")'.
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||
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||
If you are using the GNU version of termcap, you can alternatively
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||
ask `tgetent' to allocate enough space. Pass a null pointer for
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BUFFER, and `tgetent' itself allocates the storage using `malloc'.
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||
There is no way to get the address that was allocated, and you
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||
shouldn't try to free the storage.
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||
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||
With the Unix version of termcap, you must allocate space for the
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description yourself and pass the address of the space as the argument
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BUFFER. There is no way you can tell how much space is needed, so the
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convention is to allocate a buffer 2048 characters long and assume that
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||
is enough. (Formerly the convention was to allocate 1024 characters and
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assume that was enough. But one day, for one kind of terminal, that was
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not enough.)
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No matter how the space to store the description has been obtained,
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termcap records its address internally for use when you later
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interrogate the description with `tgetnum', `tgetstr' or `tgetflag'. If
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the buffer was allocated by termcap, it will be freed by termcap too if
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you call `tgetent' again. If the buffer was provided by you, you must
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make sure that its contents remain unchanged for as long as you still
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plan to interrogate the description.
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The return value of `tgetent' is -1 if there is some difficulty
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accessing the data base of terminal types, 0 if the data base is
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accessible but the specified type is not defined in it, and some other
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value otherwise.
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Here is how you might use the function `tgetent':
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#ifdef unix
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static char term_buffer[2048];
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#else
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#define term_buffer 0
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||
#endif
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||
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init_terminal_data ()
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||
{
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||
char *termtype = getenv ("TERM");
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int success;
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||
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if (termtype == 0)
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fatal ("Specify a terminal type with `setenv TERM <yourtype>'.\n");
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success = tgetent (term_buffer, termtype);
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if (success < 0)
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fatal ("Could not access the termcap data base.\n");
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if (success == 0)
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fatal ("Terminal type `%s' is not defined.\n", termtype);
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}
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Here we assume the function `fatal' prints an error message and exits.
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||
If the environment variable `TERMCAP' is defined, its value is used
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||
to override the terminal type data base. The function `tgetent' checks
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||
the value of `TERMCAP' automatically. If the value starts with `/'
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||
then it is taken as a file name to use as the data base file, instead
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||
of `/etc/termcap' which is the standard data base. If the value does
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||
not start with `/' then it is itself used as the terminal description,
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||
provided that the terminal type TERMTYPE is among the types it claims
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||
to apply to. *Note Data Base::, for information on the format of a
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||
terminal description.
|
||
|
||
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||
File: termcap.info, Node: Interrogate, Next: Initialize, Prev: Find, Up: Library
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||
|
||
Interrogating the Terminal Description
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||
======================================
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||
|
||
Each piece of information recorded in a terminal description is
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||
called a "capability". Each defined terminal capability has a
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||
two-letter code name and a specific meaning. For example, the number
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of columns is named `co'. *Note Capabilities::, for definitions of all
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the standard capability names.
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||
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||
Once you have found the proper terminal description with `tgetent'
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||
(*note Find::.), your application program must "interrogate" it for
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various terminal capabilities. You must specify the two-letter code of
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the capability whose value you seek.
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||
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||
Capability values can be numeric, boolean (capability is either
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present or absent) or strings. Any particular capability always has
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||
the same value type; for example, `co' always has a numeric value,
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while `am' (automatic wrap at margin) is always a flag, and `cm'
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||
(cursor motion command) always has a string value. The documentation
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of each capability says which type of value it has.
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||
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There are three functions to use to get the value of a capability,
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depending on the type of value the capability has. Here are their
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declarations in ANSI C:
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int tgetnum (char *NAME);
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int tgetflag (char *NAME);
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char *tgetstr (char *NAME, char **AREA);
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`tgetnum'
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Use `tgetnum' to get a capability value that is numeric. The
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argument NAME is the two-letter code name of the capability. If
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||
the capability is present, `tgetnum' returns the numeric value
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||
(which is nonnegative). If the capability is not mentioned in the
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terminal description, `tgetnum' returns -1.
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||
|
||
`tgetflag'
|
||
Use `tgetflag' to get a boolean value. If the capability NAME is
|
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present in the terminal description, `tgetflag' returns 1;
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||
otherwise, it returns 0.
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||
|
||
`tgetstr'
|
||
Use `tgetstr' to get a string value. It returns a pointer to a
|
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string which is the capability value, or a null pointer if the
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capability is not present in the terminal description.
|
||
|
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There are two ways `tgetstr' can find space to store the string
|
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value:
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||
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* You can ask `tgetstr' to allocate the space. Pass a null
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pointer for the argument AREA, and `tgetstr' will use
|
||
`malloc' to allocate storage big enough for the value.
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Termcap will never free this storage or refer to it again; you
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should free it when you are finished with it.
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||
|
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This method is more robust, since there is no need to guess
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how much space is needed. But it is supported only by the GNU
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termcap library.
|
||
|
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* You can provide the space. Provide for the argument AREA the
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address of a pointer variable of type `char *'. Before
|
||
calling `tgetstr', initialize the variable to point at
|
||
available space. Then `tgetstr' will store the string value
|
||
in that space and will increment the pointer variable to
|
||
point after the space that has been used. You can use the
|
||
same pointer variable for many calls to `tgetstr'.
|
||
|
||
There is no way to determine how much space is needed for a
|
||
single string, and no way for you to prevent or handle
|
||
overflow of the area you have provided. However, you can be
|
||
sure that the total size of all the string values you will
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||
obtain from the terminal description is no greater than the
|
||
size of the description (unless you get the same capability
|
||
twice). You can determine that size with `strlen' on the
|
||
buffer you provided to `tgetent'. See below for an example.
|
||
|
||
Providing the space yourself is the only method supported by
|
||
the Unix version of termcap.
|
||
|
||
Note that you do not have to specify a terminal type or terminal
|
||
description for the interrogation functions. They automatically use the
|
||
description found by the most recent call to `tgetent'.
|
||
|
||
Here is an example of interrogating a terminal description for
|
||
various capabilities, with conditionals to select between the Unix and
|
||
GNU methods of providing buffer space.
|
||
|
||
char *tgetstr ();
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||
|
||
char *cl_string, *cm_string;
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||
int height;
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int width;
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int auto_wrap;
|
||
|
||
char PC; /* For tputs. */
|
||
char *BC; /* For tgoto. */
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||
char *UP;
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||
|
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interrogate_terminal ()
|
||
{
|
||
#ifdef UNIX
|
||
/* Here we assume that an explicit term_buffer
|
||
was provided to tgetent. */
|
||
char *buffer
|
||
= (char *) malloc (strlen (term_buffer));
|
||
#define BUFFADDR &buffer
|
||
#else
|
||
#define BUFFADDR 0
|
||
#endif
|
||
|
||
char *temp;
|
||
|
||
/* Extract information we will use. */
|
||
cl_string = tgetstr ("cl", BUFFADDR);
|
||
cm_string = tgetstr ("cm", BUFFADDR);
|
||
auto_wrap = tgetflag ("am");
|
||
height = tgetnum ("li");
|
||
width = tgetnum ("co");
|
||
|
||
/* Extract information that termcap functions use. */
|
||
temp = tgetstr ("pc", BUFFADDR);
|
||
PC = temp ? *temp : 0;
|
||
BC = tgetstr ("le", BUFFADDR);
|
||
UP = tgetstr ("up", BUFFADDR);
|
||
}
|
||
|
||
*Note Padding::, for information on the variable `PC'. *Note Using
|
||
Parameters::, for information on `UP' and `BC'.
|
||
|
||
|
||
File: termcap.info, Node: Initialize, Next: Padding, Prev: Interrogate, Up: Library
|
||
|
||
Initialization for Use of Termcap
|
||
=================================
|
||
|
||
Before starting to output commands to a terminal using termcap, an
|
||
application program should do two things:
|
||
|
||
* Initialize various global variables which termcap library output
|
||
functions refer to. These include `PC' and `ospeed' for padding
|
||
(*note Output Padding::.) and `UP' and `BC' for cursor motion
|
||
(*note tgoto::.).
|
||
|
||
* Tell the kernel to turn off alteration and padding of
|
||
horizontal-tab characters sent to the terminal.
|
||
|
||
To turn off output processing in Berkeley Unix you would use `ioctl'
|
||
with code `TIOCLSET' to set the bit named `LLITOUT', and clear the bits
|
||
`ANYDELAY' using `TIOCSETN'. In POSIX or System V, you must clear the
|
||
bit named `OPOST'. Refer to the system documentation for details.
|
||
|
||
If you do not set the terminal flags properly, some older terminals
|
||
will not work. This is because their commands may contain the
|
||
characters that normally signify newline, carriage return and
|
||
horizontal tab--characters which the kernel thinks it ought to modify
|
||
before output.
|
||
|
||
When you change the kernel's terminal flags, you must arrange to
|
||
restore them to their normal state when your program exits. This
|
||
implies that the program must catch fatal signals such as `SIGQUIT' and
|
||
`SIGINT' and restore the old terminal flags before actually terminating.
|
||
|
||
Modern terminals' commands do not use these special characters, so
|
||
if you do not care about problems with old terminals, you can leave the
|
||
kernel's terminal flags unaltered.
|
||
|
||
|
||
File: termcap.info, Node: Padding, Next: Parameters, Prev: Initialize, Up: Library
|
||
|
||
Padding
|
||
=======
|
||
|
||
"Padding" means outputting null characters following a terminal
|
||
display command that takes a long time to execute. The terminal
|
||
description says which commands require padding and how much; the
|
||
function `tputs', described below, outputs a terminal command while
|
||
extracting from it the padding information, and then outputs the
|
||
padding that is necessary.
|
||
|
||
* Menu:
|
||
|
||
* Why Pad:: Explanation of padding.
|
||
* Not Enough:: When there is not enough padding.
|
||
* Describe Padding:: The data base says how much padding a terminal needs.
|
||
* Output Padding:: Using `tputs' to output the needed padding.
|
||
|
||
|
||
File: termcap.info, Node: Why Pad, Next: Not Enough, Up: Padding
|
||
|
||
Why Pad, and How
|
||
----------------
|
||
|
||
Most types of terminal have commands that take longer to execute
|
||
than they do to send over a high-speed line. For example, clearing the
|
||
screen may take 20msec once the entire command is received. During
|
||
that time, on a 9600 bps line, the terminal could receive about 20
|
||
additional output characters while still busy clearing the screen.
|
||
Every terminal has a certain amount of buffering capacity to remember
|
||
output characters that cannot be processed yet, but too many slow
|
||
commands in a row can cause the buffer to fill up. Then any additional
|
||
output that cannot be processed immediately will be lost.
|
||
|
||
To avoid this problem, we normally follow each display command with
|
||
enough useless charaters (usually null characters) to fill up the time
|
||
that the display command needs to execute. This does the job if the
|
||
terminal throws away null characters without using up space in the
|
||
buffer (which most terminals do). If enough padding is used, no output
|
||
can ever be lost. The right amount of padding avoids loss of output
|
||
without slowing down operation, since the time used to transmit padding
|
||
is time that nothing else could be done.
|
||
|
||
The number of padding characters needed for an operation depends on
|
||
the line speed. In fact, it is proportional to the line speed. A 9600
|
||
baud line transmits about one character per msec, so the clear screen
|
||
command in the example above would need about 20 characters of padding.
|
||
At 1200 baud, however, only about 3 characters of padding are needed
|
||
to fill up 20msec.
|
||
|
||
|
||
File: termcap.info, Node: Not Enough, Next: Describe Padding, Prev: Why Pad, Up: Padding
|
||
|
||
When There Is Not Enough Padding
|
||
--------------------------------
|
||
|
||
There are several common manifestations of insufficient padding.
|
||
|
||
* Emacs displays `I-search: ^Q-' at the bottom of the screen.
|
||
|
||
This means that the terminal thought its buffer was getting full of
|
||
display commands, so it tried to tell the computer to stop sending
|
||
any.
|
||
|
||
* The screen is garbled intermittently, or the details of garbling
|
||
vary when you repeat the action. (A garbled screen could be due
|
||
to a command which is simply incorrect, or to user option in the
|
||
terminal which doesn't match the assumptions of the terminal
|
||
description, but this usually leads to reproducible failure.)
|
||
|
||
This means that the buffer did get full, and some commands were
|
||
lost. Many changeable factors can change which ones are lost.
|
||
|
||
* Screen is garbled at high output speeds but not at low speeds.
|
||
Padding problems nearly always go away at low speeds, usually even
|
||
at 1200 baud.
|
||
|
||
This means that a high enough speed permits commands to arrive
|
||
faster than they can be executed.
|
||
|
||
Although any obscure command on an obscure terminal might lack
|
||
padding, in practice problems arise most often from the clearing
|
||
commands `cl' and `cd' (*note Clearing::.), the scrolling commands `sf'
|
||
and `sr' (*note Scrolling::.), and the line insert/delete commands `al'
|
||
and `dl' (*note Insdel Line::.).
|
||
|
||
Occasionally the terminal description fails to define `sf' and some
|
||
programs will use `do' instead, so you may get a problem with `do'. If
|
||
so, first define `sf' just like `do', then add some padding to `sf'.
|
||
|
||
The best strategy is to add a lot of padding at first, perhaps 200
|
||
msec. This is much more than enough; in fact, it should cause a
|
||
visible slowdown. (If you don't see a slowdown, the change has not
|
||
taken effect; *note Changing::..) If this makes the problem go away,
|
||
you have found the right place to add padding; now reduce the amount
|
||
until the problem comes back, then increase it again. If the problem
|
||
remains, either it is in some other capability or it is not a matter of
|
||
padding at all.
|
||
|
||
Keep in mind that on many terminals the correct padding for
|
||
insert/delete line or for scrolling is cursor-position dependent. If
|
||
you get problems from scrolling a large region of the screen but not
|
||
from scrolling a small part (just a few lines moving), it may mean that
|
||
fixed padding should be replaced with position-dependent padding.
|
||
|
||
|
||
File: termcap.info, Node: Describe Padding, Next: Output Padding, Prev: Not Enough, Up: Padding
|
||
|
||
Specifying Padding in a Terminal Description
|
||
--------------------------------------------
|
||
|
||
In the terminal description, the amount of padding required by each
|
||
display command is recorded as a sequence of digits at the front of the
|
||
command. These digits specify the padding time in milliseconds (msec).
|
||
They can be followed optionally by a decimal point and one more digit,
|
||
which is a number of tenths of msec.
|
||
|
||
Sometimes the padding needed by a command depends on the cursor
|
||
position. For example, the time taken by an "insert line" command is
|
||
usually proportional to the number of lines that need to be moved down
|
||
or cleared. An asterisk (`*') following the padding time says that the
|
||
time should be multiplied by the number of screen lines affected by the
|
||
command.
|
||
|
||
:al=1.3*\E[L:
|
||
|
||
is used to describe the "insert line" command for a certain terminal.
|
||
The padding required is 1.3 msec per line affected. The command itself
|
||
is `ESC [ L'.
|
||
|
||
The padding time specified in this way tells `tputs' how many pad
|
||
characters to output. *Note Output Padding::.
|
||
|
||
Two special capability values affect padding for all commands.
|
||
These are the `pc' and `pb'. The variable `pc' specifies the character
|
||
to pad with, and `pb' the speed below which no padding is needed. The
|
||
defaults for these variables, a null character and 0, are correct for
|
||
most terminals. *Note Pad Specs::.
|
||
|
||
|
||
File: termcap.info, Node: Output Padding, Prev: Describe Padding, Up: Padding
|
||
|
||
Performing Padding with `tputs'
|
||
-------------------------------
|
||
|
||
Use the termcap function `tputs' to output a string containing an
|
||
optional padding spec of the form described above (*note Describe
|
||
Padding::.). The function `tputs' strips off and decodes the padding
|
||
spec, outputs the rest of the string, and then outputs the appropriate
|
||
padding. Here is its declaration in ANSI C:
|
||
|
||
char PC;
|
||
short ospeed;
|
||
|
||
int tputs (char *STRING, int NLINES, int (*OUTFUN) ());
|
||
|
||
Here STRING is the string (including padding spec) to be output;
|
||
NLINES is the number of lines affected by the operation, which is used
|
||
to multiply the amount of padding if the padding spec ends with a `*'.
|
||
Finally, OUTFUN is a function (such as `fputchar') that is called to
|
||
output each character. When actually called, OUTFUN should expect one
|
||
argument, a character.
|
||
|
||
The operation of `tputs' is controlled by two global variables,
|
||
`ospeed' and `PC'. The value of `ospeed' is supposed to be the
|
||
terminal output speed, encoded as in the `ioctl' system call which gets
|
||
the speed information. This is needed to compute the number of padding
|
||
characters. The value of `PC' is the character used for padding.
|
||
|
||
You are responsible for storing suitable values into these variables
|
||
before using `tputs'. The value stored into the `PC' variable should be
|
||
taken from the `pc' capability in the terminal description (*note Pad
|
||
Specs::.). Store zero in `PC' if there is no `pc' capability.
|
||
|
||
The argument NLINES requires some thought. Normally, it should be
|
||
the number of lines whose contents will be cleared or moved by the
|
||
command. For cursor motion commands, or commands that do editing
|
||
within one line, use the value 1. For most commands that affect
|
||
multiple lines, such as `al' (insert a line) and `cd' (clear from the
|
||
cursor to the end of the screen), NLINES should be the screen height
|
||
minus the current vertical position (origin 0). For multiple insert
|
||
and scroll commands such as `AL' (insert multiple lines), that same
|
||
value for NLINES is correct; the number of lines being inserted is not
|
||
correct.
|
||
|
||
If a "scroll window" feature is used to reduce the number of lines
|
||
affected by a command, the value of NLINES should take this into
|
||
account. This is because the delay time required depends on how much
|
||
work the terminal has to do, and the scroll window feature reduces the
|
||
work. *Note Scrolling::.
|
||
|
||
Commands such as `ic' and `dc' (insert or delete characters) are
|
||
problematical because the padding needed by these commands is
|
||
proportional to the number of characters affected, which is the number
|
||
of columns from the cursor to the end of the line. It would be nice to
|
||
have a way to specify such a dependence, and there is no need for
|
||
dependence on vertical position in these commands, so it is an obvious
|
||
idea to say that for these commands NLINES should really be the number
|
||
of columns affected. However, the definition of termcap clearly says
|
||
that NLINES is always the number of lines affected, even in this case,
|
||
where it is always 1. It is not easy to change this rule now, because
|
||
too many programs and terminal descriptions have been written to follow
|
||
it.
|
||
|
||
Because NLINES is always 1 for the `ic' and `dc' strings, there is
|
||
no reason for them to use `*', but some of them do. These should be
|
||
corrected by deleting the `*'. If, some day, such entries have
|
||
disappeared, it may be possible to change to a more useful convention
|
||
for the NLINES argument for these operations without breaking any
|
||
programs.
|
||
|
||
|
||
File: termcap.info, Node: Parameters, Prev: Padding, Up: Library
|
||
|
||
Filling In Parameters
|
||
=====================
|
||
|
||
Some terminal control strings require numeric "parameters". For
|
||
example, when you move the cursor, you need to say what horizontal and
|
||
vertical positions to move it to. The value of the terminal's `cm'
|
||
capability, which says how to move the cursor, cannot simply be a
|
||
string of characters; it must say how to express the cursor position
|
||
numbers and where to put them within the command.
|
||
|
||
The specifications of termcap include conventions as to which
|
||
string-valued capabilities require parameters, how many parameters, and
|
||
what the parameters mean; for example, it defines the `cm' string to
|
||
take two parameters, the vertical and horizontal positions, with 0,0
|
||
being the upper left corner. These conventions are described where the
|
||
individual commands are documented.
|
||
|
||
Termcap also defines a language used within the capability
|
||
definition for specifying how and where to encode the parameters for
|
||
output. This language uses character sequences starting with `%'.
|
||
(This is the same idea as `printf', but the details are different.)
|
||
The language for parameter encoding is described in this section.
|
||
|
||
A program that is doing display output calls the functions `tparam'
|
||
or `tgoto' to encode parameters according to the specifications. These
|
||
functions produce a string containing the actual commands to be output
|
||
(as well a padding spec which must be processed with `tputs'; *note
|
||
Padding::.).
|
||
|
||
* Menu:
|
||
|
||
* Encode Parameters:: The language for encoding parameters.
|
||
* Using Parameters:: Outputting a string command with parameters.
|
||
|
||
|
||
File: termcap.info, Node: Encode Parameters, Next: Using Parameters, Up: Parameters
|
||
|
||
Describing the Encoding
|
||
-----------------------
|
||
|
||
A terminal command string that requires parameters contains special
|
||
character sequences starting with `%' to say how to encode the
|
||
parameters. These sequences control the actions of `tparam' and
|
||
`tgoto'.
|
||
|
||
The parameters values passed to `tparam' or `tgoto' are considered
|
||
to form a vector. A pointer into this vector determines the next
|
||
parameter to be processed. Some of the `%'-sequences encode one
|
||
parameter and advance the pointer to the next parameter. Other
|
||
`%'-sequences alter the pointer or alter the parameter values without
|
||
generating output.
|
||
|
||
For example, the `cm' string for a standard ANSI terminal is written
|
||
as `\E[%i%d;%dH'. (`\E' stands for ESC.) `cm' by convention always
|
||
requires two parameters, the vertical and horizontal goal positions, so
|
||
this string specifies the encoding of two parameters. Here `%i'
|
||
increments the two values supplied, and each `%d' encodes one of the
|
||
values in decimal. If the cursor position values 20,58 are encoded
|
||
with this string, the result is `\E[21;59H'.
|
||
|
||
First, here are the `%'-sequences that generate output. Except for
|
||
`%%', each of them encodes one parameter and advances the pointer to
|
||
the following parameter.
|
||
|
||
`%%'
|
||
Output a single `%'. This is the only way to represent a literal
|
||
`%' in a terminal command with parameters. `%%' does not use up a
|
||
parameter.
|
||
|
||
`%d'
|
||
As in `printf', output the next parameter in decimal.
|
||
|
||
`%2'
|
||
Like `%02d' in `printf': output the next parameter in decimal, and
|
||
always use at least two digits.
|
||
|
||
`%3'
|
||
Like `%03d' in `printf': output the next parameter in decimal, and
|
||
always use at least three digits. Note that `%4' and so on are
|
||
*not* defined.
|
||
|
||
`%.'
|
||
Output the next parameter as a single character whose ASCII code is
|
||
the parameter value. Like `%c' in `printf'.
|
||
|
||
`%+CHAR'
|
||
Add the next parameter to the character CHAR, and output the
|
||
resulting character. For example, `%+ ' represents 0 as a space,
|
||
1 as `!', etc.
|
||
|
||
The following `%'-sequences specify alteration of the parameters
|
||
(their values, or their order) rather than encoding a parameter for
|
||
output. They generate no output; they are used only for their side
|
||
effects on the parameters. Also, they do not advance the "next
|
||
parameter" pointer except as explicitly stated. Only `%i', `%r' and
|
||
`%>' are defined in standard Unix termcap. The others are GNU
|
||
extensions.
|
||
|
||
`%i'
|
||
Increment the next two parameters. This is used for terminals that
|
||
expect cursor positions in origin 1. For example, `%i%d,%d' would
|
||
output two parameters with `1' for 0, `2' for 1, etc.
|
||
|
||
`%r'
|
||
Interchange the next two parameters. This is used for terminals
|
||
whose cursor positioning command expects the horizontal position
|
||
first.
|
||
|
||
`%s'
|
||
Skip the next parameter. Do not output anything.
|
||
|
||
`%b'
|
||
Back up one parameter. The last parameter used will become once
|
||
again the next parameter to be output, and the next output command
|
||
will use it. Using `%b' more than once, you can back up any
|
||
number of parameters, and you can refer to each parameter any
|
||
number of times.
|
||
|
||
`%>C1C2'
|
||
Conditionally increment the next parameter. Here C1 and C2 are
|
||
characters which stand for their ASCII codes as numbers. If the
|
||
next parameter is greater than the ASCII code of C1, the ASCII
|
||
code of C2 is added to it.
|
||
|
||
`%a OP TYPE POS'
|
||
Perform arithmetic on the next parameter, do not use it up, and do
|
||
not output anything. Here OP specifies the arithmetic operation,
|
||
while TYPE and POS together specify the other operand.
|
||
|
||
Spaces are used above to separate the operands for clarity; the
|
||
spaces don't appear in the data base, where this sequence is
|
||
exactly five characters long.
|
||
|
||
The character OP says what kind of arithmetic operation to
|
||
perform. It can be any of these characters:
|
||
|
||
`='
|
||
assign a value to the next parameter, ignoring its old value.
|
||
The new value comes from the other operand.
|
||
|
||
`+'
|
||
add the other operand to the next parameter.
|
||
|
||
`-'
|
||
subtract the other operand from the next parameter.
|
||
|
||
`*'
|
||
multiply the next parameter by the other operand.
|
||
|
||
`/'
|
||
divide the next parameter by the other operand.
|
||
|
||
The "other operand" may be another parameter's value or a constant;
|
||
the character TYPE says which. It can be:
|
||
|
||
`p'
|
||
Use another parameter. The character POS says which
|
||
parameter to use. Subtract 64 from its ASCII code to get the
|
||
position of the desired parameter relative to this one. Thus,
|
||
the character `A' as POS means the parameter after the next
|
||
one; the character `?' means the parameter before the next
|
||
one.
|
||
|
||
`c'
|
||
Use a constant value. The character POS specifies the value
|
||
of the constant. The 0200 bit is cleared out, so that 0200
|
||
can be used to represent zero.
|
||
|
||
The following `%'-sequences are special purpose hacks to compensate
|
||
for the weird designs of obscure terminals. They modify the next
|
||
parameter or the next two parameters but do not generate output and do
|
||
not use up any parameters. `%m' is a GNU extension; the others are
|
||
defined in standard Unix termcap.
|
||
|
||
`%n'
|
||
Exclusive-or the next parameter with 0140, and likewise the
|
||
parameter after next.
|
||
|
||
`%m'
|
||
Complement all the bits of the next parameter and the parameter
|
||
after next.
|
||
|
||
`%B'
|
||
Encode the next parameter in BCD. It alters the value of the
|
||
parameter by adding six times the quotient of the parameter by ten.
|
||
Here is a C statement that shows how the new value is computed:
|
||
|
||
PARM = (PARM / 10) * 16 + PARM % 10;
|
||
|
||
`%D'
|
||
Transform the next parameter as needed by Delta Data terminals.
|
||
This involves subtracting twice the remainder of the parameter by
|
||
16.
|
||
|
||
PARM -= 2 * (PARM % 16);
|
||
|
||
|
||
File: termcap.info, Node: Using Parameters, Prev: Encode Parameters, Up: Parameters
|
||
|
||
Sending Display Commands with Parameters
|
||
----------------------------------------
|
||
|
||
The termcap library functions `tparam' and `tgoto' serve as the
|
||
analog of `printf' for terminal string parameters. The newer function
|
||
`tparam' is a GNU extension, more general but missing from Unix
|
||
termcap. The original parameter-encoding function is `tgoto', which is
|
||
preferable for cursor motion.
|
||
|
||
* Menu:
|
||
|
||
* tparam:: The general case, for GNU termcap only.
|
||
* tgoto:: The special case of cursor motion.
|
||
|
||
|
||
File: termcap.info, Node: tparam, Next: tgoto, Up: Using Parameters
|
||
|
||
`tparam'
|
||
........
|
||
|
||
The function `tparam' can encode display commands with any number of
|
||
parameters and allows you to specify the buffer space. It is the
|
||
preferred function for encoding parameters for all but the `cm'
|
||
capability. Its ANSI C declaration is as follows:
|
||
|
||
char *tparam (char *CTLSTRING, char *BUFFER, int SIZE, int PARM1,...)
|
||
|
||
The arguments are a control string CTLSTRING (the value of a terminal
|
||
capability, presumably), an output buffer BUFFER and SIZE, and any
|
||
number of integer parameters to be encoded. The effect of `tparam' is
|
||
to copy the control string into the buffer, encoding parameters
|
||
according to the `%' sequences in the control string.
|
||
|
||
You describe the output buffer by its address, BUFFER, and its size
|
||
in bytes, SIZE. If the buffer is not big enough for the data to be
|
||
stored in it, `tparam' calls `malloc' to get a larger buffer. In
|
||
either case, `tparam' returns the address of the buffer it ultimately
|
||
uses. If the value equals BUFFER, your original buffer was used.
|
||
Otherwise, a new buffer was allocated, and you must free it after you
|
||
are done with printing the results. If you pass zero for SIZE and
|
||
BUFFER, `tparam' always allocates the space with `malloc'.
|
||
|
||
All capabilities that require parameters also have the ability to
|
||
specify padding, so you should use `tputs' to output the string
|
||
produced by `tparam'. *Note Padding::. Here is an example.
|
||
|
||
{
|
||
char *buf;
|
||
char buffer[40];
|
||
|
||
buf = tparam (command, buffer, 40, parm);
|
||
tputs (buf, 1, fputchar);
|
||
if (buf != buffer)
|
||
free (buf);
|
||
}
|
||
|
||
If a parameter whose value is zero is encoded with `%.'-style
|
||
encoding, the result is a null character, which will confuse `tputs'.
|
||
This would be a serious problem, but luckily `%.' encoding is used only
|
||
by a few old models of terminal, and only for the `cm' capability. To
|
||
solve the problem, use `tgoto' rather than `tparam' to encode the `cm'
|
||
capability.
|
||
|
||
|
||
File: termcap.info, Node: tgoto, Prev: tparam, Up: Using Parameters
|
||
|
||
`tgoto'
|
||
.......
|
||
|
||
The special case of cursor motion is handled by `tgoto'. There are
|
||
two reasons why you might choose to use `tgoto':
|
||
|
||
* For Unix compatibility, because Unix termcap does not have
|
||
`tparam'.
|
||
|
||
* For the `cm' capability, since `tgoto' has a special feature to
|
||
avoid problems with null characters, tabs and newlines on certain
|
||
old terminal types that use `%.' encoding for that capability.
|
||
|
||
Here is how `tgoto' might be declared in ANSI C:
|
||
|
||
char *tgoto (char *CSTRING, int HPOS, int VPOS)
|
||
|
||
There are three arguments, the terminal description's `cm' string and
|
||
the two cursor position numbers; `tgoto' computes the parametrized
|
||
string in an internal static buffer and returns the address of that
|
||
buffer. The next time you use `tgoto' the same buffer will be reused.
|
||
|
||
Parameters encoded with `%.' encoding can generate null characters,
|
||
tabs or newlines. These might cause trouble: the null character because
|
||
`tputs' would think that was the end of the string, the tab because the
|
||
kernel or other software might expand it into spaces, and the newline
|
||
becaue the kernel might add a carriage-return, or padding characters
|
||
normally used for a newline. To prevent such problems, `tgoto' is
|
||
careful to avoid these characters. Here is how this works: if the
|
||
target cursor position value is such as to cause a problem (that is to
|
||
say, zero, nine or ten), `tgoto' increments it by one, then compensates
|
||
by appending a string to move the cursor back or up one position.
|
||
|
||
The compensation strings to use for moving back or up are found in
|
||
global variables named `BC' and `UP'. These are actual external C
|
||
variables with upper case names; they are declared `char *'. It is up
|
||
to you to store suitable values in them, normally obtained from the
|
||
`le' and `up' terminal capabilities in the terminal description with
|
||
`tgetstr'. Alternatively, if these two variables are both zero, the
|
||
feature of avoiding nulls, tabs and newlines is turned off.
|
||
|
||
It is safe to use `tgoto' for commands other than `cm' only if you
|
||
have stored zero in `BC' and `UP'.
|
||
|
||
Note that `tgoto' reverses the order of its operands: the horizontal
|
||
position comes before the vertical position in the arguments to
|
||
`tgoto', even though the vertical position comes before the horizontal
|
||
in the parameters of the `cm' string. If you use `tgoto' with a
|
||
command such as `AL' that takes one parameter, you must pass the
|
||
parameter to `tgoto' as the "vertical position".
|
||
|
||
|
||
File: termcap.info, Node: Data Base, Next: Capabilities, Prev: Library, Up: Top
|
||
|
||
The Format of the Data Base
|
||
***************************
|
||
|
||
The termcap data base of terminal descriptions is stored in the file
|
||
`/etc/termcap'. It contains terminal descriptions, blank lines, and
|
||
comments.
|
||
|
||
A terminal description starts with one or more names for the
|
||
terminal type. The information in the description is a series of
|
||
"capability names" and values. The capability names have standard
|
||
meanings (*note Capabilities::.) and their values describe the terminal.
|
||
|
||
* Menu:
|
||
|
||
* Format:: Overall format of a terminal description.
|
||
* Capability Format:: Format of capabilities within a description.
|
||
* Naming:: Naming conventions for terminal types.
|
||
* Inheriting:: Inheriting part of a description from
|
||
a related terminal type.
|
||
* Changing:: When changes in the data base take effect.
|
||
|
||
|
||
File: termcap.info, Node: Format, Next: Capability Format, Up: Data Base
|
||
|
||
Terminal Description Format
|
||
===========================
|
||
|
||
Aside from comments (lines starting with `#', which are ignored),
|
||
each nonblank line in the termcap data base is a terminal description.
|
||
A terminal description is nominally a single line, but it can be split
|
||
into multiple lines by inserting the two characters `\ newline'. This
|
||
sequence is ignored wherever it appears in a description.
|
||
|
||
The preferred way to split the description is between capabilities:
|
||
insert the four characters `: \ newline tab' immediately before any
|
||
colon. This allows each sub-line to start with some indentation. This
|
||
works because, after the `\ newline' are ignored, the result is `: tab
|
||
:'; the first colon ends the preceding capability and the second colon
|
||
starts the next capability. If you split with `\ newline' alone, you
|
||
may not add any indentation after them.
|
||
|
||
Here is a real example of a terminal description:
|
||
|
||
dw|vt52|DEC vt52:\
|
||
:cr=^M:do=^J:nl=^J:bl=^G:\
|
||
:le=^H:bs:cd=\EJ:ce=\EK:cl=\EH\EJ:\
|
||
:cm=\EY%+ %+ :co#80:li#24:\
|
||
:nd=\EC:ta=^I:pt:sr=\EI:up=\EA:\
|
||
:ku=\EA:kd=\EB:kr=\EC:kl=\ED:kb=^H:
|
||
|
||
Each terminal description begins with several names for the terminal
|
||
type. The names are separated by `|' characters, and a colon ends the
|
||
last name. The first name should be two characters long; it exists
|
||
only for the sake of very old Unix systems and is never used in modern
|
||
systems. The last name should be a fully verbose name such as "DEC
|
||
vt52" or "Ann Arbor Ambassador with 48 lines". The other names should
|
||
include whatever the user ought to be able to specify to get this
|
||
terminal type, such as `vt52' or `aaa-48'. *Note Naming::, for
|
||
information on how to choose terminal type names.
|
||
|
||
After the terminal type names come the terminal capabilities,
|
||
separated by colons and with a colon after the last one. Each
|
||
capability has a two-letter name, such as `cm' for "cursor motion
|
||
string" or `li' for "number of display lines".
|
||
|
||
|
||
File: termcap.info, Node: Capability Format, Next: Naming, Prev: Format, Up: Data Base
|
||
|
||
Writing the Capabilities
|
||
========================
|
||
|
||
There are three kinds of capabilities: flags, numbers, and strings.
|
||
Each kind has its own way of being written in the description. Each
|
||
defined capability has by convention a particular kind of value; for
|
||
example, `li' always has a numeric value and `cm' always a string value.
|
||
|
||
A flag capability is thought of as having a boolean value: the value
|
||
is true if the capability is present, false if not. When the
|
||
capability is present, just write its name between two colons.
|
||
|
||
A numeric capability has a value which is a nonnegative number.
|
||
Write the capability name, a `#', and the number, between two colons.
|
||
For example, `...:li#48:...' is how you specify the `li' capability for
|
||
48 lines.
|
||
|
||
A string-valued capability has a value which is a sequence of
|
||
characters. Usually these are the characters used to perform some
|
||
display operation. Write the capability name, a `=', and the
|
||
characters of the value, between two colons. For example,
|
||
`...:cm=\E[%i%d;%dH:...' is how the cursor motion command for a
|
||
standard ANSI terminal would be specified.
|
||
|
||
Special characters in the string value can be expressed using
|
||
`\'-escape sequences as in C; in addition, `\E' stands for ESC. `^' is
|
||
also a kind of escape character; `^' followed by CHAR stands for the
|
||
control-equivalent of CHAR. Thus, `^a' stands for the character
|
||
control-a, just like `\001'. `\' and `^' themselves can be represented
|
||
as `\\' and `\^'.
|
||
|
||
To include a colon in the string, you must write `\072'. You might
|
||
ask, "Why can't `\:' be used to represent a colon?" The reason is that
|
||
the interrogation functions do not count slashes while looking for a
|
||
capability. Even if `:ce=ab\:cd:' were interpreted as giving the `ce'
|
||
capability the value `ab:cd', it would also appear to define `cd' as a
|
||
flag.
|
||
|
||
The string value will often contain digits at the front to specify
|
||
padding (*note Padding::.) and/or `%'-sequences within to specify how
|
||
to encode parameters (*note Parameters::.). Although these things are
|
||
not to be output literally to the terminal, they are considered part of
|
||
the value of the capability. They are special only when the string
|
||
value is processed by `tputs', `tparam' or `tgoto'. By contrast, `\'
|
||
and `^' are considered part of the syntax for specifying the characters
|
||
in the string.
|
||
|
||
Let's look at the VT52 example again:
|
||
|
||
dw|vt52|DEC vt52:\
|
||
:cr=^M:do=^J:nl=^J:bl=^G:\
|
||
:le=^H:bs:cd=\EJ:ce=\EK:cl=\EH\EJ:\
|
||
:cm=\EY%+ %+ :co#80:li#24:\
|
||
:nd=\EC:ta=^I:pt:sr=\EI:up=\EA:\
|
||
:ku=\EA:kd=\EB:kr=\EC:kl=\ED:kb=^H:
|
||
|
||
Here we see the numeric-valued capabilities `co' and `li', the flags
|
||
`bs' and `pt', and many string-valued capabilities. Most of the
|
||
strings start with ESC represented as `\E'. The rest contain control
|
||
characters represented using `^'. The meanings of the individual
|
||
capabilities are defined elsewhere (*note Capabilities::.).
|
||
|