1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
|
<!--
****************************************************************************
* Copyright 2018-2023,2024 Thomas E. Dickey *
* Copyright 2017 Free Software Foundation, Inc. *
* *
* Permission is hereby granted, free of charge, to any person obtaining a *
* copy of this software and associated documentation files (the *
* "Software"), to deal in the Software without restriction, including *
* without limitation the rights to use, copy, modify, merge, publish, *
* distribute, distribute with modifications, sublicense, and/or sell *
* copies of the Software, and to permit persons to whom the Software is *
* furnished to do so, subject to the following conditions: *
* *
* The above copyright notice and this permission notice shall be included *
* in all copies or substantial portions of the Software. *
* *
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS *
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF *
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. *
* IN NO EVENT SHALL THE ABOVE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, *
* DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR *
* OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR *
* THE USE OR OTHER DEALINGS IN THE SOFTWARE. *
* *
* Except as contained in this notice, the name(s) of the above copyright *
* holders shall not be used in advertising or otherwise to promote the *
* sale, use or other dealings in this Software without prior written *
* authorization. *
****************************************************************************
* @Id: scr_dump.5,v 1.46 2024/03/23 20:42:29 tom Exp @
-->
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN">
<HTML>
<HEAD>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
<meta name="generator" content="Manpage converted by man2html - see https://invisible-island.net/scripts/readme.html#others_scripts">
<TITLE>scr_dump 5 2024-03-23 ncurses 6.5 File formats</TITLE>
<link rel="author" href="mailto:bug-ncurses@gnu.org">
</HEAD>
<BODY>
<H1 class="no-header">scr_dump 5 2024-03-23 ncurses 6.5 File formats</H1>
<PRE>
<STRONG><A HREF="scr_dump.5.html">scr_dump(5)</A></STRONG> File formats <STRONG><A HREF="scr_dump.5.html">scr_dump(5)</A></STRONG>
</PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
scr_dump - <EM>curses</EM> screen dump
</PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
The curses library provides applications with the ability to write the
contents of a window to an external file using <STRONG>scr_dump</STRONG> or <STRONG>putwin</STRONG>, and
read it back using <STRONG>scr_restore</STRONG> or <STRONG>getwin</STRONG>.
The <STRONG>putwin</STRONG> and <STRONG>getwin</STRONG> functions do the work; while <STRONG>scr_dump</STRONG> and
<STRONG>scr_restore</STRONG> conveniently save and restore the whole screen, i.e.,
<STRONG>stdscr</STRONG>.
</PRE><H3><a name="h3-ncurses6">ncurses6</a></H3><PRE>
A longstanding implementation of screen-dump was revised with ncurses6
to remedy problems with the earlier approach:
<STRONG>o</STRONG> A "magic number" is written to the beginning of the dump file,
allowing applications (such as <STRONG>file(1)</STRONG>) to recognize curses dump
files.
Because ncurses6 uses a new format, that requires a new magic
number was unused by other applications. This 16-bit number was
unused:
0x8888 (octal "\210\210")
but to be more certain, this 32-bit number was chosen:
0x88888888 (octal "\210\210\210\210")
This is the pattern submitted to the maintainers of the <STRONG>file</STRONG>
program:
#
# ncurses5 (and before) did not use a magic number,
# making screen dumps "data".
#
# ncurses6 (2015) uses this format, ignoring byte-order
0 string \210\210\210\210ncurses ncurses6 screen image
#
<STRONG>o</STRONG> The screen dumps are written in textual form, so that internal data
sizes are not directly related to the dump-format, and enabling the
library to read dumps from either narrow- or wide-character-
configurations.
The <EM>narrow</EM> library configuration holds characters and video
attributes in a 32-bit <STRONG>chtype</STRONG>, while the <EM>wide-character</EM> library
stores this information in the <STRONG>cchar_t</STRONG> structure, which is much
larger than 32-bits.
<STRONG>o</STRONG> It is possible to read a screen dump into a terminal with a
different screen-size, because the library truncates or fills the
screen as necessary.
<STRONG>o</STRONG> The ncurses6 <STRONG>getwin</STRONG> reads the legacy screen dumps from ncurses5.
</PRE><H3><a name="h3-ncurses5-_Legacy_">ncurses5 (Legacy)</a></H3><PRE>
The screen-dump feature was added to <EM>ncurses</EM> in June 1995. While there
were fixes and improvements in succeeding years, the basic scheme was
unchanged:
<STRONG>o</STRONG> The <EM>WINDOW</EM> structure was written in binary form.
<STRONG>o</STRONG> The <EM>WINDOW</EM> structure refers to lines of data, which were written as
an array of binary data following the <EM>WINDOW</EM>.
<STRONG>o</STRONG> When <STRONG>getwin</STRONG> restored the window, it would keep track of offsets
into the array of line-data and adjust the <EM>WINDOW</EM> structure which
was read back into memory.
This is similar to Unix System V, but does not write a "magic number"
to identify the file format.
</PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
There is no standard format for <EM>curses</EM> screen dumps. A brief survey of
the existing implementations follows.
</PRE><H3><a name="h3-X_Open-Curses">X/Open Curses</a></H3><PRE>
X/Open Curses, Issue 7 specifies little. It says (boldface emphasis
added)
"[t]he <EM>getwin()</EM> function reads window-related data stored in the
file by <EM>putwin()</EM>. The function then creates and initializes a new
window using that data.
The <EM>putwin()</EM> function writes all data associated with <EM>win</EM> into the
<EM>stdio</EM> stream to which <EM>filep</EM> points, using an <STRONG>unspecified</STRONG> <STRONG>format</STRONG>.
This information can be retrieved later using <EM>getwin()</EM>."
In the mid-1990s when the X/Open Curses document was written, there
were still System V systems using older, less capable <EM>curses</EM> libraries.
BSD <EM>curses</EM> was not relevant to X/Open because it did not meet the
criteria for base-level conformance; see <STRONG><A HREF="ncurses.3x.html">ncurses(3x)</A></STRONG>.
</PRE><H3><a name="h3-System-V">System V</a></H3><PRE>
System V <EM>curses</EM> identified the file format by writing a "magic number"
at the beginning of the dump. The <EM>WINDOW</EM> data and the lines of text
follow, all in binary form.
Solaris <EM>curses</EM> has the following definitions.
/* terminfo magic number */
#define MAGNUM 0432
/* curses screen dump magic number */
#define SVR2_DUMP_MAGIC_NUMBER 0433
#define SVR3_DUMP_MAGIC_NUMBER 0434
That is, the feature was likely introduced in SVr2 (1984), and improved
in SVr3 (1987). Solaris <EM>curses</EM> has no magic number for SVr4 (1989).
Other System V operating systems (AIX and HP-UX) use a magic number
that would correspond to the following.
/* curses screen dump magic number */
#define SVR4_DUMP_MAGIC_NUMBER 0435
That octal number in bytes is 001, 035. Because most Unix vendors at
the time used big-endian hardware, the magic number is written with the
high-order byte first.
\001\035
After the magic number, the <EM>WINDOW</EM> structure and line data are written
in binary format. While the magic number used by these systems can be
observed with <STRONG>od(1)</STRONG>, none of them documents the format used for screen
dumps.
Nor do they use an identical format, even with the System V family.
The <EM>ncurses</EM> <EM>savescreen</EM> test program was used to collect information for
this manual page. It produced dumps of different size (all on 64-bit
hardware, on 40x80 screens):
<STRONG>o</STRONG> AIX (51817 bytes)
<STRONG>o</STRONG> HP-UX (90093 bytes)
<STRONG>o</STRONG> Solaris 10 (13273 bytes)
<STRONG>o</STRONG> <EM>ncurses</EM>5 (12888 bytes)
</PRE><H3><a name="h3-Solaris">Solaris</a></H3><PRE>
As noted above, Solaris <EM>curses</EM> has no magic number corresponding to
SVr4 <EM>curses</EM>. This is odd, since Solaris was the first operating system
to meet the SVr4 guidelines. Solaris furthermore supplies two versions
of <EM>curses</EM>.
<STRONG>o</STRONG> The default <EM>curses</EM> library uses the SVr3 magic number.
<STRONG>o</STRONG> An alternate <EM>curses</EM> library (which we term <EM>xcurses),</EM> available in
<EM>/usr/xpg4</EM>, uses a textual format with no magic number.
According to its copyright notice, this <EM>xcurses</EM> library was
developed by MKS (Mortice Kern Systems) from 1990 to 1995.
Like ncurses6, it includes a header with parameters. Unlike
ncurses6, the contents of the window are written piecemeal, with
coordinates and attributes for each chunk of text rather than
writing the whole window from top to bottom.
</PRE><H3><a name="h3-PDCurses">PDCurses</a></H3><PRE>
<EM>PDCurses</EM> added support for screen dumps in version 2.7 (2005). Like
System V and ncurses5, it writes the <EM>WINDOW</EM> structure in binary, but
begins the file with its three-byte identifier "PDC", followed by a
single-byte version number.
"PDC\001"
</PRE><H3><a name="h3-NetBSD">NetBSD</a></H3><PRE>
As of April 2017, NetBSD <EM>curses</EM> does not support <STRONG>scr_dump</STRONG> and
<STRONG>scr_restore</STRONG> (or <STRONG>scr_init</STRONG>, <STRONG>scr_set</STRONG>), although it has <STRONG>putwin</STRONG> and <STRONG>getwin</STRONG>.
Like ncurses5, NetBSD <STRONG>putwin</STRONG> does not identify its dumps with a useful
magic number. It writes
<STRONG>o</STRONG> the <EM>curses</EM> shared library major and minor versions as the first two
bytes (for example, 7 and 1),
<STRONG>o</STRONG> followed by a binary dump of the <EM>WINDOW</EM>,
<STRONG>o</STRONG> some data for wide characters referenced by the <EM>WINDOW</EM> structure,
and
<STRONG>o</STRONG> finally, lines as done by other implementations.
</PRE><H2><a name="h2-EXAMPLES">EXAMPLES</a></H2><PRE>
Given a simple program which writes text to the screen (and for the
sake of example, limiting the screen-size to 10x20):
#include <curses.h>
int
main(void)
{
putenv("LINES=10");
putenv("COLUMNS=20");
initscr();
start_color();
init_pair(1, COLOR_WHITE, COLOR_BLUE);
init_pair(2, COLOR_RED, COLOR_BLACK);
bkgd(<STRONG>COLOR_PAIR(1)</STRONG>);
move(4, 5);
attron(A_BOLD);
addstr("Hello");
move(5, 5);
attroff(A_BOLD);
attrset(A_REVERSE | <STRONG>COLOR_PAIR(2)</STRONG>);
addstr("World!");
refresh();
scr_dump("foo.out");
endwin();
return 0;
}
When run using ncurses6, the output looks like this:
\210\210\210\210ncurses 6.0.20170415
_cury=5
_curx=11
_maxy=9
_maxx=19
_flags=14
_attrs=\{REVERSE|C2}
flag=_idcok
_delay=-1
_regbottom=9
_bkgrnd=\{NORMAL|C1}\s
rows:
1:\{NORMAL|C1}\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s
2:\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s
3:\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s
4:\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s
5:\s\s\s\s\s\{BOLD}Hello\{NORMAL}\s\s\s\s\s\s\s\s\s\s
6:\s\s\s\s\s\{REVERSE|C2}World!\{NORMAL|C1}\s\s\s\s\s\s\s\s\s
7:\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s
8:\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s
9:\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s
10:\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s
The first four octal escapes are actually nonprinting characters, while
the remainder of the file is printable text. You may notice:
<STRONG>o</STRONG> The actual color pair values are not written to the file.
<STRONG>o</STRONG> All characters are shown in printable form; spaces are "\s" to
ensure they are not overlooked.
<STRONG>o</STRONG> Attributes are written in escaped curly braces, e.g., "\{BOLD}",
and may include a color pair (C1 or C2 in this example).
<STRONG>o</STRONG> The parameters in the header are written out only if they are
nonzero. When reading back, order does not matter.
Running the same program with Solaris <EM>xpg4</EM> curses gives this dump:
MAX=10,20
BEG=0,0
SCROLL=0,10
VMIN=1
VTIME=0
FLAGS=0x1000
FG=0,0
BG=0,0,
0,0,0,1,
0,19,0,0,
1,0,0,1,
1,19,0,0,
2,0,0,1,
2,19,0,0,
3,0,0,1,
3,19,0,0,
4,0,0,1,
4,5,0x20,0,Hello
4,10,0,1,
4,19,0,0,
5,0,0,1,
5,5,0x4,2,World!
5,11,0,1,
5,19,0,0,
6,0,0,1,
6,19,0,0,
7,0,0,1,
7,19,0,0,
8,0,0,1,
8,19,0,0,
9,0,0,1,
9,19,0,0,
CUR=11,5
Solaris <STRONG>getwin</STRONG> requires that all parameters are present, and in the
same order. The <EM>xpg4</EM> curses library does not know about the <STRONG>bce</STRONG> (back
color erase) capability, and does not color the window background.
On the other hand, the SVr4 curses library does know about the
background color. However, its screen dumps are in binary. Here is
the corresponding dump (using "od -t x1"):
0000000 1c 01 c3 d6 f3 58 05 00 0b 00 0a 00 14 00 00 00
0000020 00 00 02 00 00 00 00 00 00 00 00 00 00 00 00 00
0000040 00 00 b8 1a 06 08 cc 1a 06 08 00 00 09 00 10 00
0000060 00 00 00 80 00 00 20 00 00 00 ff ff ff ff 00 00
0000100 ff ff ff ff 00 00 00 00 20 80 00 00 20 80 00 00
0000120 20 80 00 00 20 80 00 00 20 80 00 00 20 80 00 00
*
0000620 20 80 00 00 20 80 00 00 20 80 00 00 48 80 00 04
0000640 65 80 00 04 6c 80 00 04 6c 80 00 04 6f 80 00 04
0000660 20 80 00 00 20 80 00 00 20 80 00 00 20 80 00 00
*
0000740 20 80 00 00 20 80 00 00 20 80 00 00 57 00 81 00
0000760 6f 00 81 00 72 00 81 00 6c 00 81 00 64 00 81 00
0001000 21 00 81 00 20 80 00 00 20 80 00 00 20 80 00 00
0001020 20 80 00 00 20 80 00 00 20 80 00 00 20 80 00 00
*
0001540 20 80 00 00 20 80 00 00 00 00 f6 d1 01 00 f6 d1
0001560 08 00 00 00 40 00 00 00 00 00 00 00 00 00 00 07
0001600 00 04 00 01 00 01 00 00 00 01 00 00 00 00 00 00
0001620 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
*
0002371
</PRE><H2><a name="h2-AUTHORS">AUTHORS</a></H2><PRE>
Thomas E. Dickey
extended screen-dump format for <EM>ncurses</EM> 6.0 (2015)
Eric S. Raymond
screen dump feature in <EM>ncurses</EM> 1.9.2d (1995)
</PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
<STRONG><A HREF="curs_scr_dump.3x.html">curs_scr_dump(3x)</A></STRONG>, <STRONG><A HREF="curs_util.3x.html">curs_util(3x)</A></STRONG>
ncurses 6.5 2024-03-23 <STRONG><A HREF="scr_dump.5.html">scr_dump(5)</A></STRONG>
</PRE>
<div class="nav">
<ul>
<li><a href="#h2-NAME">NAME</a></li>
<li><a href="#h2-DESCRIPTION">DESCRIPTION</a>
<ul>
<li><a href="#h3-ncurses6">ncurses6</a></li>
<li><a href="#h3-ncurses5-_Legacy_">ncurses5 (Legacy)</a></li>
</ul>
</li>
<li><a href="#h2-PORTABILITY">PORTABILITY</a>
<ul>
<li><a href="#h3-X_Open-Curses">X/Open Curses</a></li>
<li><a href="#h3-System-V">System V</a></li>
<li><a href="#h3-Solaris">Solaris</a></li>
<li><a href="#h3-PDCurses">PDCurses</a></li>
<li><a href="#h3-NetBSD">NetBSD</a></li>
</ul>
</li>
<li><a href="#h2-EXAMPLES">EXAMPLES</a></li>
<li><a href="#h2-AUTHORS">AUTHORS</a></li>
<li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>
</ul>
</div>
</BODY>
</HTML>
|
