1 This is Info file ./termcap.info, produced by Makeinfo-1.55 from the
2 input file ./termcap.texi.
4 This file documents the termcap library of the GNU system.
6 Copyright (C) 1988 Free Software Foundation, Inc.
8 Permission is granted to make and distribute verbatim copies of this
9 manual provided the copyright notice and this permission notice are
10 preserved on all copies.
12 Permission is granted to copy and distribute modified versions of
13 this manual under the conditions for verbatim copying, provided that
14 the entire resulting derived work is distributed under the terms of a
15 permission notice identical to this one.
17 Permission is granted to copy and distribute translations of this
18 manual into another language, under the above conditions for modified
19 versions, except that this permission notice may be stated in a
20 translation approved by the Foundation.
23 File: termcap.info, Node: Naming, Next: Inheriting, Prev: Capability Format, Up: Data Base
25 Terminal Type Name Conventions
26 ==============================
28 There are conventions for choosing names of terminal types. For one
29 thing, all letters should be in lower case. The terminal type for a
30 terminal in its most usual or most fundamental mode of operation should
31 not have a hyphen in it.
33 If the same terminal has other modes of operation which require
34 different terminal descriptions, these variant descriptions are given
35 names made by adding suffixes with hyphens. Such alternate descriptions
36 are used for two reasons:
38 * When the terminal has a switch that changes its behavior. Since
39 the computer cannot tell how the switch is set, the user must tell
40 the computer by choosing the appropriate terminal type name.
42 For example, the VT-100 has a setup flag that controls whether the
43 cursor wraps at the right margin. If this flag is set to "wrap",
44 you must use the terminal type `vt100-am'. Otherwise you must use
45 `vt100-nam'. Plain `vt100' is defined as a synonym for either
46 `vt100-am' or `vt100-nam' depending on the preferences of the
49 The standard suffix `-am' stands for "automatic margins".
51 * To give the user a choice in how to use the terminal. This is done
52 when the terminal has a switch that the computer normally controls.
54 For example, the Ann Arbor Ambassador can be configured with many
55 screen sizes ranging from 20 to 60 lines. Fewer lines make bigger
56 characters but more lines let you see more of what you are editing.
57 As a result, users have different preferences. Therefore, termcap
58 provides terminal types for many screen sizes. If you choose type
59 `aaa-30', the terminal will be configured to use 30 lines; if you
60 choose `aaa-48', 48 lines will be used, and so on.
62 Here is a list of standard suffixes and their conventional meanings:
65 Short for "wide". This is a mode that gives the terminal more
66 columns than usual. This is normally a user option.
69 "Automatic margins". This is an alternate description for use when
70 the terminal's margin-wrap switch is on; it contains the `am'
71 flag. The implication is that normally the switch is off and the
72 usual description for the terminal says that the switch is off.
75 "No automatic margins". The opposite of `-am', this names an
76 alternative description which lacks the `am' flag. This implies
77 that the terminal is normally operated with the margin-wrap switch
78 turned on, and the normal description of the terminal says so.
81 "No arrows". This terminal description initializes the terminal to
82 keep its arrow keys in local mode. This is a user option.
85 "Reverse video". This terminal description causes text output for
86 normal video to appear as reverse, and text output for reverse
87 video to come out as normal. Often this description differs from
88 the usual one by interchanging the two strings which turn reverse
91 This is a user option; you can choose either the "reverse video"
92 variant terminal type or the normal terminal type, and termcap will
96 "Status". Says to enable use of a status line which ordinary
97 output does not touch (*note Status Line::.).
99 Some terminals have a special line that is used only as a status
100 line. For these terminals, there is no need for an `-s' variant;
101 the status line commands should be defined by default. On other
102 terminals, enabling a status line means removing one screen line
103 from ordinary use and reducing the effective screen height. For
104 these terminals, the user can choose the `-s' variant type to
105 request use of a status line.
108 Says to operate with NLINES lines on the screen, for terminals
109 such as the Ambassador which provide this as an option. Normally
110 this is a user option; by choosing the terminal type, you control
111 how many lines termcap will use.
114 Says that the terminal has NPAGES pages worth of screen memory,
115 for terminals where this is a hardware option.
118 Says that description is not for direct use, but only for
119 reference in `tc' capabilities. Such a description is a kind of
120 subroutine, because it describes the common characteristics of
121 several variant descriptions that would use other suffixes in
125 File: termcap.info, Node: Inheriting, Next: Changing, Prev: Naming, Up: Data Base
127 Inheriting from Related Descriptions
128 ====================================
130 When two terminal descriptions are similar, their identical parts do
131 not need to be given twice. Instead, one of the two can be defined in
132 terms of the other, using the `tc' capability. We say that one
133 description "refers to" the other, or "inherits from" the other.
135 The `tc' capability must be the last one in the terminal description,
136 and its value is a string which is the name of another terminal type
137 which is referred to. For example,
139 N9|aaa|ambassador|aaa-30|ann arbor ambassador/30 lines:\
140 :ti=\E[2J\E[30;0;0;30p:\
141 :te=\E[60;0;0;30p\E[30;1H\E[J:\
144 defines the terminal type `aaa-30' (also known as plain `aaa') in terms
145 of `aaa-unk', which defines everything about the Ambassador that is
146 independent of screen height. The types `aaa-36', `aaa-48' and so on
147 for other screen heights are likewise defined to inherit from `aaa-unk'.
149 The capabilities overridden by `aaa-30' include `li', which says how
150 many lines there are, and `ti' and `te', which configure the terminal
151 to use that many lines.
153 The effective terminal description for type `aaa' consists of the
154 text shown above followed by the text of the description of `aaa-unk'.
155 The `tc' capability is handled automatically by `tgetent', which finds
156 the description thus referenced and combines the two descriptions
157 (*note Find::.). Therefore, only the implementor of the terminal
158 descriptions needs to think about using `tc'. Users and application
159 programmers do not need to be concerned with it.
161 Since the reference terminal description is used last, capabilities
162 specified in the referring description override any specifications of
163 the same capabilities in the reference description.
165 The referring description can cancel out a capability without
166 specifying any new value for it by means of a special trick. Write the
167 capability in the referring description, with the character `@' after
168 the capability name, as follows:
170 NZ|aaa-30-nam|ann arbor ambassador/30 lines/no automatic-margins:\
174 File: termcap.info, Node: Changing, Prev: Inheriting, Up: Data Base
176 When Changes in the Data Base Take Effect
177 =========================================
179 Each application program must read the terminal description from the
180 data base, so a change in the data base is effective for all jobs
181 started after the change is made.
183 The change will usually have no effect on a job that have been in
184 existence since before the change. The program probably read the
185 terminal description once, when it was started, and is continuing to
186 use what it read then. If the program does not have a feature for
187 reexamining the data base, then you will need to run it again (probably
188 killing the old job).
190 If the description in use is coming from the `TERMCAP' environment
191 variable, then the data base file is effectively overridden, and
192 changes in it will have no effect until you change the `TERMCAP'
193 variable as well. For example, some users' `.login' files
194 automatically copy the terminal description into `TERMCAP' to speed
195 startup of applications. If you have done this, you will need to
196 change the `TERMCAP' variable to make the changed data base take effect.
199 File: termcap.info, Node: Capabilities, Next: Summary, Prev: Data Base, Up: Top
201 Definitions of the Terminal Capabilities
202 ****************************************
204 This section is divided into many subsections, each for one aspect of
205 use of display terminals. For writing a display program, you usually
206 need only check the subsections for the operations you want to use.
207 For writing a terminal description, you must read each subsection and
208 fill in the capabilities described there.
210 String capabilities that are display commands may require numeric
211 parameters (*note Parameters::.). Most such capabilities do not use
212 parameters. When a capability requires parameters, this is explicitly
213 stated at the beginning of its definition. In simple cases, the first
214 or second sentence of the definition mentions all the parameters, in
215 the order they should be given, using a name in upper case for each
216 one. For example, the `rp' capability is a command that requires two
217 parameters; its definition begins as follows:
219 String of commands to output a graphic character C, repeated N
222 In complex cases or when there are many parameters, they are
223 described explicitly.
225 When a capability is described as obsolete, this means that programs
226 should not be written to look for it, but terminal descriptions should
227 still be written to provide it.
229 When a capability is described as very obsolete, this means that it
230 should be omitted from terminal descriptions as well.
234 * Basic:: Basic characteristics.
235 * Screen Size:: Screen size, and what happens when it changes.
236 * Cursor Motion:: Various ways to move the cursor.
237 * Wrapping:: What happens if you write a character in the last column.
238 * Scrolling:: Pushing text up and down on the screen.
239 * Windows:: Limiting the part of the window that output affects.
240 * Clearing:: Erasing one or many lines.
241 * Insdel Line:: Making new blank lines in mid-screen; deleting lines.
242 * Insdel Char:: Inserting and deleting characters within a line.
243 * Standout:: Highlighting some of the text.
244 * Underlining:: Underlining some of the text.
245 * Cursor Visibility:: Making the cursor more or less easy to spot.
246 * Bell:: Attracts user's attention; not localized on the screen.
247 * Keypad:: Recognizing when function keys or arrows are typed.
248 * Meta Key:: META acts like an extra shift key.
249 * Initialization:: Commands used to initialize or reset the terminal.
250 * Pad Specs:: Info for the kernel on how much padding is needed.
251 * Status Line:: A status line displays "background" information.
252 * Half-Line:: Moving by half-lines, for superscripts and subscripts.
253 * Printer:: Controlling auxiliary printers of display terminals.
256 File: termcap.info, Node: Basic, Next: Screen Size, Up: Capabilities
258 Basic Characteristics
259 =====================
261 This section documents the capabilities that describe the basic and
262 nature of the terminal, and also those that are relevant to the output
263 of graphic characters.
266 Flag whose presence means that the terminal can overstrike. This
267 means that outputting a graphic character does not erase whatever
268 was present in the same character position before. The terminals
269 that can overstrike include printing terminals, storage tubes (all
270 obsolete nowadays), and many bit-map displays.
273 Flag whose presence means that outputting a space erases a
274 character position even if the terminal supports overstriking. If
275 this flag is not present and overstriking is supported, output of
276 a space has no effect except to move the cursor.
278 (On terminals that do not support overstriking, you can always
279 assume that outputting a space at a position erases whatever
280 character was previously displayed there.)
283 Flag whose presence means that this terminal type is a generic type
284 which does not really describe any particular terminal. Generic
285 types are intended for use as the default type assigned when the
286 user connects to the system, with the intention that the user
287 should specify what type he really has. One example of a generic
288 type is the type `network'.
290 Since the generic type cannot say how to do anything interesting
291 with the terminal, termcap-using programs will always find that the
292 terminal is too weak to be supported if the user has failed to
293 specify a real terminal type in place of the generic one. The
294 `gn' flag directs these programs to use a different error message:
295 "You have not specified your real terminal type", rather than
296 "Your terminal is not powerful enough to be used".
299 Flag whose presence means this is a hardcopy terminal.
302 String of commands to output a graphic character C, repeated N
303 times. The first parameter value is the ASCII code for the desired
304 character, and the second parameter is the number of times to
305 repeat the character. Often this command requires padding
306 proportional to the number of times the character is repeated.
307 This effect can be had by using parameter arithmetic with
308 `%'-sequences to compute the amount of padding, then generating
309 the result as a number at the front of the string so that `tputs'
310 will treat it as padding.
313 Flag whose presence means that the ASCII character `~' cannot be
314 output on this terminal because it is used for display commands.
316 Programs handle this flag by checking all text to be output and
317 replacing each `~' with some other character(s). If this is not
318 done, the screen will be thoroughly garbled.
320 The old Hazeltine terminals that required such treatment are
321 probably very rare today, so you might as well not bother to
325 String whose presence means the terminal has a settable command
326 character. The value of the string is the default command
327 character (which is usually ESC).
329 All the strings of commands in the terminal description should be
330 written to use the default command character. If you are writing
331 an application program that changes the command character, use the
332 `CC' capability to figure out how to translate all the display
333 commands to work with the new command character.
335 Most programs have no reason to look at the `CC' capability.
338 Flag whose presence identifies Superbee terminals which are unable
339 to transmit the characters ESC and `Control-C'. Programs which
340 support this flag are supposed to check the input for the code
341 sequences sent by the F1 and F2 keys, and pretend that ESC or
342 `Control-C' (respectively) had been read. But this flag is
343 obsolete, and not worth supporting.
346 File: termcap.info, Node: Screen Size, Next: Cursor Motion, Prev: Basic, Up: Capabilities
351 A terminal description has two capabilities, `co' and `li', that
352 describe the screen size in columns and lines. But there is more to
353 the question of screen size than this.
355 On some operating systems the "screen" is really a window and the
356 effective width can vary. On some of these systems, `tgetnum' uses the
357 actual width of the window to decide what value to return for the `co'
358 capability, overriding what is actually written in the terminal
359 description. On other systems, it is up to the application program to
360 check the actual window width using a system call. For example, on BSD
361 4.3 systems, the system call `ioctl' with code `TIOCGWINSZ' will tell
362 you the current screen size.
364 On all window systems, termcap is powerless to advise the application
365 program if the user resizes the window. Application programs must deal
366 with this possibility in a system-dependent fashion. On some systems
367 the C shell handles part of the problem by detecting changes in window
368 size and setting the `TERMCAP' environment variable appropriately.
369 This takes care of application programs that are started subsequently.
370 It does not help application programs already running.
372 On some systems, including BSD 4.3, all programs using a terminal get
373 a signal named `SIGWINCH' whenever the screen size changes. Programs
374 that use termcap should handle this signal by using `ioctl TIOCGWINSZ'
375 to learn the new screen size.
378 Numeric value, the width of the screen in character positions.
379 Even hardcopy terminals normally have a `co' capability.
382 Numeric value, the height of the screen in lines.
385 File: termcap.info, Node: Cursor Motion, Next: Wrapping, Prev: Screen Size, Up: Capabilities
390 Termcap assumes that the terminal has a "cursor", a spot on the
391 screen where a visible mark is displayed, and that most display
392 commands take effect at the position of the cursor. It follows that
393 moving the cursor to a specified location is very important.
395 There are many terminal capabilities for different cursor motion
396 operations. A terminal description should define as many as possible,
397 but most programs do not need to use most of them. One capability,
398 `cm', moves the cursor to an arbitrary place on the screen; this by
399 itself is sufficient for any application as long as there is no need to
400 support hardcopy terminals or certain old, weak displays that have only
401 relative motion commands. Use of other cursor motion capabilities is an
402 optimization, enabling the program to output fewer characters in some
405 If you plan to use the relative cursor motion commands in an
406 application program, you must know what the starting cursor position
407 is. To do this, you must keep track of the cursor position and update
408 the records each time anything is output to the terminal, including
409 graphic characters. In addition, it is necessary to know whether the
410 terminal wraps after writing in the rightmost column. *Note Wrapping::.
412 One other motion capability needs special mention: `nw' moves the
413 cursor to the beginning of the following line, perhaps clearing all the
414 starting line after the cursor, or perhaps not clearing at all. This
415 capability is a least common denominator that is probably supported
416 even by terminals that cannot do most other things such as `cm' or `do'.
417 Even hardcopy terminals can support `nw'.
420 String of commands to position the cursor at line L, column C.
421 Both parameters are origin-zero, and are defined relative to the
422 screen, not relative to display memory.
424 All display terminals except a few very obsolete ones support `cm',
425 so it is acceptable for an application program to refuse to
426 operate on terminals lacking `cm'.
429 String of commands to move the cursor to the upper left corner of
430 the screen (this position is called the "home position"). In
431 terminals where the upper left corner of the screen is not the
432 same as the beginning of display memory, this command must go to
433 the upper left corner of the screen, not the beginning of display
436 Every display terminal supports this capability, and many
437 application programs refuse to operate if the `ho' capability is
441 String of commands to move the cursor to the lower left corner of
442 the screen. On some terminals, moving up from home position does
443 this, but programs should never assume that will work. Just
444 output the `ll' string (if it is provided); if moving to home
445 position and then moving up is the best way to get there, the `ll'
446 command will do that.
449 String of commands to move the cursor to the beginning of the line
450 it is on. If this capability is not specified, many programs
451 assume they can use the ASCII carriage return character for this.
454 String of commands to move the cursor left one column. Unless the
455 `bw' flag capability is specified, the effect is undefined if the
456 cursor is at the left margin; do not use this command there. If
457 `bw' is present, this command may be used at the left margin, and
458 it wraps the cursor to the last column of the preceding line.
461 String of commands to move the cursor right one column. The
462 effect is undefined if the cursor is at the right margin; do not
463 use this command there, not even if `am' is present.
466 String of commands to move the cursor vertically up one line. The
467 effect of sending this string when on the top line is undefined;
468 programs should never use it that way.
471 String of commands to move the cursor vertically down one line.
472 The effect of sending this string when on the bottom line is
473 undefined; programs should never use it that way.
475 Some programs do use `do' to scroll up one line if used at the
476 bottom line, if `sf' is not defined but `sr' is. This is only to
477 compensate for certain old, incorrect terminal descriptions. (In
478 principle this might actually lead to incorrect behavior on other
479 terminals, but that seems to happen rarely if ever.) But the
480 proper solution is that the terminal description should define
481 `sf' as well as `do' if the command is suitable for scrolling.
483 The original idea was that this string would not contain a newline
484 character and therefore could be used without disabling the
485 kernel's usual habit of converting of newline into a
486 carriage-return newline sequence. But many terminal descriptions
487 do use newline in the `do' string, so this is not possible; a
488 program which sends the `do' string must disable output conversion
489 in the kernel (*note Initialize::.).
492 Flag whose presence says that `le' may be used in column zero to
493 move to the last column of the preceding line. If this flag is
494 not present, `le' should not be used in column zero.
497 String of commands to move the cursor to start of next line,
498 possibly clearing rest of line (following the cursor) before
501 `DO', `UP', `LE', `RI'
502 Strings of commands to move the cursor N lines down vertically, up
503 vertically, or N columns left or right. Do not attempt to move
504 past any edge of the screen with these commands; the effect of
505 trying that is undefined. Only a few terminal descriptions provide
506 these commands, and most programs do not use them.
509 String of commands to position the cursor at line L, column C,
510 relative to display memory. Both parameters are origin-zero.
511 This capability is present only in terminals where there is a
512 difference between screen-relative and memory-relative addressing,
513 and not even in all such terminals.
516 String of commands to position the cursor at column C in the same
517 line it is on. This is a special case of `cm' in which the
518 vertical position is not changed. The `ch' capability is provided
519 only when it is faster to output than `cm' would be in this
520 special case. Programs should not assume most display terminals
524 String of commands to position the cursor at line L in the same
525 column. This is a special case of `cm' in which the horizontal
526 position is not changed. The `cv' capability is provided only
527 when it is faster to output than `cm' would be in this special
528 case. Programs should not assume most display terminals have `cv'.
531 String of commands to make the terminal save the current cursor
532 position. Only the last saved position can be used. If this
533 capability is present, `rc' should be provided also. Most
534 terminals have neither.
537 String of commands to make the terminal restore the last saved
538 cursor position. If this capability is present, `sc' should be
539 provided also. Most terminals have neither.
542 String of commands to advance to the next page, for a hardcopy
546 String of commands to move the cursor right to the next hardware
547 tab stop column. Missing if the terminal does not have any kind of
548 hardware tabs. Do not send this command if the kernel's terminal
549 modes say that the kernel is expanding tabs into spaces.
552 String of commands to move the cursor left to the previous hardware
553 tab stop column. Missing if the terminal has no such ability; many
554 terminals do not. Do not send this command if the kernel's
555 terminal modes say that the kernel is expanding tabs into spaces.
557 The following obsolete capabilities should be included in terminal
558 descriptions when appropriate, but should not be looked at by new
562 Flag whose presence means the terminal does not support the ASCII
563 carriage return character as `cr'. This flag is needed because
564 old programs assume, when the `cr' capability is missing, that
565 ASCII carriage return can be used for the purpose. We use `nc' to
566 tell the old programs that carriage return may not be used.
568 New programs should not assume any default for `cr', so they need
569 not look at `nc'. However, descriptions should contain `nc'
570 whenever they do not contain `cr'.
573 Flag whose presence means that the ASCII tab character may not be
574 used for cursor motion. This flag exists because old programs
575 assume, when the `ta' capability is missing, that ASCII tab can be
576 used for the purpose. We use `xt' to tell the old programs not to
579 New programs should not assume any default for `ta', so they need
580 not look at `xt' in connection with cursor motion. Note that `xt'
581 also has implications for standout mode (*note Standout::.). It
582 is obsolete in regard to cursor motion but not in regard to
585 In fact, `xt' means that the terminal is a Teleray 1061.
588 Very obsolete alternative name for the `le' capability.
591 Flag whose presence means that the ASCII character backspace may be
592 used to move the cursor left. Obsolete; look at `le' instead.
595 Obsolete capability which is a string that can either be used to
596 move the cursor down or to scroll. The same string must scroll
597 when used on the bottom line and move the cursor when used on any
598 other line. New programs should use `do' or `sf', and ignore `nl'.
600 If there is no `nl' capability, some old programs assume they can
601 use the newline character for this purpose. These programs follow
602 a bad practice, but because they exist, it is still desirable to
603 define the `nl' capability in a terminal description if the best
604 way to move down is *not* a newline.
607 File: termcap.info, Node: Wrapping, Next: Scrolling, Prev: Cursor Motion, Up: Capabilities
612 "Wrapping" means moving the cursor from the right margin to the left
613 margin of the following line. Some terminals wrap automatically when a
614 graphic character is output in the last column, while others do not.
615 Most application programs that use termcap need to know whether the
616 terminal wraps. There are two special flag capabilities to describe
617 what the terminal does when a graphic character is output in the last
621 Flag whose presence means that writing a character in the last
622 column causes the cursor to wrap to the beginning of the next line.
624 If `am' is not present, writing in the last column leaves the
625 cursor at the place where the character was written.
627 Writing in the last column of the last line should be avoided on
628 terminals with `am', as it may or may not cause scrolling to occur
629 (*note Scrolling::.). Scrolling is surely not what you would
632 If your program needs to check the `am' flag, then it also needs
633 to check the `xn' flag which indicates that wrapping happens in a
634 strange way. Many common terminals have the `xn' flag.
637 Flag whose presence means that the cursor wraps in a strange way.
638 At least two distinct kinds of strange behavior are known; the
639 termcap data base does not contain anything to distinguish the two.
641 On Concept-100 terminals, output in the last column wraps the
642 cursor almost like an ordinary `am' terminal. But if the next
643 thing output is a newline, it is ignored.
645 DEC VT-100 terminals (when the wrap switch is on) do a different
646 strange thing: the cursor wraps only if the next thing output is
647 another graphic character. In fact, the wrap occurs when the
648 following graphic character is received by the terminal, before the
649 character is placed on the screen.
651 On both of these terminals, after writing in the last column a
652 following graphic character will be displayed in the first column
653 of the following line. But the effect of relative cursor motion
654 characters such as newline or backspace at such a time depends on
655 the terminal. The effect of erase or scrolling commands also
656 depends on the terminal. You can't assume anything about what
657 they will do on a terminal that has `xn'. So, to be safe, you
658 should never do these things at such a time on such a terminal.
660 To be sure of reliable results on a terminal which has the `xn'
661 flag, output a `cm' absolute positioning command after writing in
662 the last column. Another safe thing to do is to output
663 carriage-return newline, which will leave the cursor at the
664 beginning of the following line.
667 Flag whose presence means that it is safe to write in the last
668 column of the last line without worrying about undesired
669 scrolling. `LP' indicates the DEC flavor of `xn' strangeness.
672 File: termcap.info, Node: Scrolling, Next: Windows, Prev: Wrapping, Up: Capabilities
677 "Scrolling" means moving the contents of the screen up or down one or
678 more lines. Moving the contents up is "forward scrolling"; moving them
679 down is "reverse scrolling".
681 Scrolling happens after each line of output during ordinary output
682 on most display terminals. But in an application program that uses
683 termcap for random-access output, scrolling happens only when
684 explicitly requested with the commands in this section.
686 Some terminals have a "scroll region" feature. This lets you limit
687 the effect of scrolling to a specified range of lines. Lines outside
688 the range are unaffected when scrolling happens. The scroll region
689 feature is available if either `cs' or `cS' is present.
692 String of commands to scroll the screen one line up, assuming it is
693 output with the cursor at the beginning of the bottom line.
696 String of commands to scroll the screen one line down, assuming it
697 is output with the cursor at the beginning of the top line.
700 A few programs will try to use `do' to do the work of `sf'. This
701 is not really correct--it is an attempt to compensate for the
702 absence of a `sf' command in some old terminal descriptions.
704 Since these terminal descriptions do define `sr', perhaps at one
705 time the definition of `do' was different and it could be used for
706 scrolling as well. But it isn't desirable to combine these two
707 functions in one capability, since scrolling often requires more
708 padding than simply moving the cursor down. Defining `sf' and
709 `do' separately allows you to specify the padding properly. Also,
710 all sources agree that `do' should not be relied on to do
713 So the best approach is to add `sf' capabilities to the
714 descriptions of these terminals, copying the definition of `do' if
718 String of commands to scroll the screen N lines up, assuming it is
719 output with the cursor at the beginning of the bottom line.
722 String of commands to scroll the screen N lines down, assuming it
723 is output with the cursor at the beginning of the top line.
726 String of commands to set the scroll region. This command takes
727 two parameters, START and END, which are the line numbers
728 (origin-zero) of the first line to include in the scroll region
729 and of the last line to include in it. When a scroll region is
730 set, scrolling is limited to the specified range of lines; lines
731 outside the range are not affected by scroll commands.
733 Do not try to move the cursor outside the scroll region. The
734 region remains set until explicitly removed. To remove the scroll
735 region, use another `cs' command specifying the full height of the
738 The cursor position is undefined after the `cs' command is set, so
739 position the cursor with `cm' immediately afterward.
742 String of commands to set the scroll region using parameters in
743 different form. The effect is the same as if `cs' were used.
744 Four parameters are required:
746 1. Total number of lines on the screen.
748 2. Number of lines above desired scroll region.
750 3. Number of lines below (outside of) desired scroll region.
752 4. Total number of lines on the screen, the same as the first
755 This capability is a GNU extension that was invented to allow the
756 Ann Arbor Ambassador's scroll-region command to be described; it
757 could also be done by putting non-Unix `%'-sequences into a `cs'
758 string, but that would have confused Unix programs that used the
759 `cs' capability with the Unix termcap. Currently only GNU Emacs
760 uses the `cS' capability.
763 Flag which means that the terminal does not normally scroll for
764 ordinary sequential output. For modern terminals, this means that
765 outputting a newline in ordinary sequential output with the cursor
766 on the bottom line wraps to the top line. For some obsolete
767 terminals, other things may happen.
769 The terminal may be able to scroll even if it does not normally do
770 so. If the `sf' capability is provided, it can be used for
771 scrolling regardless of `ns'.
774 Flag whose presence means that lines scrolled up off the top of the
775 screen may come back if scrolling down is done subsequently.
777 The `da' and `db' flags do not, strictly speaking, affect how to
778 scroll. But programs that scroll usually need to clear the lines
779 scrolled onto the screen, if these flags are present.
782 Flag whose presence means that lines scrolled down off the bottom
783 of the screen may come back if scrolling up is done subsequently.
786 Numeric value, the number of lines of display memory that the
787 terminal has. A value of zero means that the terminal has more
788 display memory than can fit on the screen, but no fixed number of
789 lines. (The number of lines may depend on the amount of text in
792 Any terminal description that defines `SF' should also define `sf';
793 likewise for `SR' and `sr'. However, many terminals can only scroll by
794 one line at a time, so it is common to find `sf' and not `SF', or `sr'
797 Therefore, all programs that use the scrolling facilities should be
798 prepared to work with `sf' in the case that `SF' is absent, and
799 likewise with `sr'. On the other hand, an application program that
800 uses only `sf' and not `SF' is acceptable, though slow on some
803 When outputting a scroll command with `tputs', the NLINES argument
804 should be the total number of lines in the portion of the screen being
805 scrolled. Very often these commands require padding proportional to
806 this number of lines. *Note Padding::.
809 File: termcap.info, Node: Windows, Next: Clearing, Prev: Scrolling, Up: Capabilities
814 A "window", in termcap, is a rectangular portion of the screen to
815 which all display operations are restricted. Wrapping, clearing,
816 scrolling, insertion and deletion all operate as if the specified
817 window were all the screen there was.
820 String of commands to set the terminal output screen window. This
821 string requires four parameters, all origin-zero:
822 1. The first line to include in the window.
824 2. The last line to include in the window.
826 3. The first column to include in the window.
828 4. The last column to include in the window.
830 Most terminals do not support windows.
833 File: termcap.info, Node: Clearing, Next: Insdel Line, Prev: Windows, Up: Capabilities
835 Clearing Parts of the Screen
836 ============================
838 There are several terminal capabilities for clearing parts of the
839 screen to blank. All display terminals support the `cl' string, and
840 most display terminals support all of these capabilities.
843 String of commands to clear the entire screen and position the
844 cursor at the upper left corner.
847 String of commands to clear the line the cursor is on, and all the
848 lines below it, down to the bottom of the screen. This command
849 string should be used only with the cursor in column zero; their
850 effect is undefined if the cursor is elsewhere.
853 String of commands to clear from the cursor to the end of the
857 String of commands to clear N characters, starting with the
858 character that the cursor is on. This command string is expected
859 to leave the cursor position unchanged. The parameter N should
860 never be large enough to reach past the right margin; the effect
861 of such a large parameter would be undefined.
863 Clear to end of line (`ce') is extremely important in programs that
864 maintain an updating display. Nearly all display terminals support this
865 operation, so it is acceptable for a an application program to refuse to
866 work if `ce' is not present. However, if you do not want this
867 limitation, you can accomplish clearing to end of line by outputting
868 spaces until you reach the right margin. In order to do this, you must
869 know the current horizontal position. Also, this technique assumes
870 that writing a space will erase. But this happens to be true on all
871 the display terminals that fail to support `ce'.
874 File: termcap.info, Node: Insdel Line, Next: Insdel Char, Prev: Clearing, Up: Capabilities
879 "Inserting a line" means creating a blank line in the middle of the
880 screen, and pushing the existing lines of text apart. In fact, the
881 lines above the insertion point do not change, while the lines below
882 move down, and one is normally lost at the bottom of the screen.
884 "Deleting a line" means causing the line to disappear from the
885 screen, closing up the gap by moving the lines below it upward. A new
886 line appears at the bottom of the screen. Usually this line is blank,
887 but on terminals with the `db' flag it may be a line previously moved
888 off the screen bottom by scrolling or line insertion.
890 Insertion and deletion of lines is useful in programs that maintain
891 an updating display some parts of which may get longer or shorter.
892 They are also useful in editors for scrolling parts of the screen, and
893 for redisplaying after lines of text are killed or inserted.
895 Many terminals provide commands to insert or delete a single line at
896 the cursor position. Some provide the ability to insert or delete
897 several lines with one command, using the number of lines to insert or
898 delete as a parameter. Always move the cursor to column zero before
899 using any of these commands.
902 String of commands to insert a blank line before the line the
903 cursor is on. The existing line, and all lines below it, are
904 moved down. The last line in the screen (or in the scroll region,
905 if one is set) disappears and in most circumstances is discarded.
906 It may not be discarded if the `db' is present (*note
909 The cursor must be at the left margin before this command is used.
910 This command does not move the cursor.
913 String of commands to delete the line the cursor is on. The
914 following lines move up, and a blank line appears at the bottom of
915 the screen (or bottom of the scroll region). If the terminal has
916 the `db' flag, a nonblank line previously pushed off the screen
917 bottom may reappear at the bottom.
919 The cursor must be at the left margin before this command is used.
920 This command does not move the cursor.
923 String of commands to insert N blank lines before the line that
924 the cursor is on. It is like `al' repeated N times, except that
925 it is as fast as one `al'.
928 String of commands to delete N lines starting with the line that
929 the cursor is on. It is like `dl' repeated N times, except that
930 it is as fast as one `dl'.
932 Any terminal description that defines `AL' should also define `al';
933 likewise for `DL' and `dl'. However, many terminals can only insert or
934 delete one line at a time, so it is common to find `al' and not `AL',
935 or `dl' without `DL'.
937 Therefore, all programs that use the insert and delete facilities
938 should be prepared to work with `al' in the case that `AL' is absent,
939 and likewise with `dl'. On the other hand, it is acceptable to write
940 an application that uses only `al' and `dl' and does not look for `AL'
943 If a terminal does not support line insertion and deletion directly,
944 but does support a scroll region, the effect of insertion and deletion
945 can be obtained with scrolling. However, it is up to the individual
946 user program to check for this possibility and use the scrolling
947 commands to get the desired result. It is fairly important to implement
948 this alternate strategy, since it is the only way to get the effect of
949 line insertion and deletion on the popular VT100 terminal.
951 Insertion and deletion of lines is affected by the scroll region on
952 terminals that have a settable scroll region. This is useful when it is
953 desirable to move any few consecutive lines up or down by a few lines.
956 The line pushed off the bottom of the screen is not lost if the
957 terminal has the `db' flag capability; instead, it is pushed into
958 display memory that does not appear on the screen. This is the same
959 thing that happens when scrolling pushes a line off the bottom of the
960 screen. Either reverse scrolling or deletion of a line can bring the
961 apparently lost line back onto the bottom of the screen. If the
962 terminal has the scroll region feature as well as `db', the pushed-out
963 line really is lost if a scroll region is in effect.
965 When outputting an insert or delete command with `tputs', the NLINES
966 argument should be the total number of lines from the cursor to the
967 bottom of the screen (or scroll region). Very often these commands
968 require padding proportional to this number of lines. *Note Padding::.
970 For `AL' and `DL' the NLINES argument should *not* depend on the
971 number of lines inserted or deleted; only the total number of lines
972 affected. This is because it is just as fast to insert two or N lines
973 with `AL' as to insert one line with `al'.
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