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29 * @Id: scr_dump.5,v 1.15 2018/07/28 21:46:15 tom Exp @
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41 <H1 class="no-header">scr_dump 5</H1>
43 <STRONG><A HREF="scr_dump.5.html">scr_dump(5)</A></STRONG> File Formats Manual <STRONG><A HREF="scr_dump.5.html">scr_dump(5)</A></STRONG>
48 </PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
49 scr_dump - format of curses screen-dumps.
52 </PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
53 <STRONG>scr_dump</STRONG>
56 </PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
57 The curses library provides applications with the ability to write the
58 contents of a window to an external file using <STRONG>scr_dump</STRONG> or <STRONG>putwin</STRONG>, and
59 read it back using <STRONG>scr_restore</STRONG> or <STRONG>getwin</STRONG>.
61 The <STRONG>putwin</STRONG> and <STRONG>getwin</STRONG> functions do the work; while <STRONG>scr_dump</STRONG> and
62 <STRONG>scr_restore</STRONG> conveniently save and restore the whole screen, i.e., <STRONG>std-</STRONG>
66 </PRE><H3><a name="h3-ncurses6">ncurses6</a></H3><PRE>
67 A longstanding implementation of screen-dump was revised with ncurses6
68 to remedy problems with the earlier approach:
70 <STRONG>o</STRONG> A "magic number" is written to the beginning of the dump file,
71 allowing applications (such as <STRONG>file(1)</STRONG>) to recognize curses dump
74 Because ncurses6 uses a new format, that requires a new magic num-
75 ber was unused by other applications. This 16-bit number was
78 0x8888 (octal "\210\210")
80 but to be more certain, this 32-bit number was chosen:
82 0x88888888 (octal "\210\210\210\210")
84 This is the pattern submitted to the maintainers of the <STRONG>file</STRONG> pro-
88 # ncurses5 (and before) did not use a magic number,
89 # making screen dumps "data".
91 # ncurses6 (2015) uses this format, ignoring byte-order
92 0 string \210\210\210\210ncurses ncurses6 screen image
95 <STRONG>o</STRONG> The screen dumps are written in textual form, so that internal data
96 sizes are not directly related to the dump-format, and enabling the
97 library to read dumps from either narrow- or wide-character- con-
100 The <EM>narrow</EM> library configuration holds characters and video
101 attributes in a 32-bit <STRONG>chtype</STRONG>, while the <EM>wide-character</EM> library
102 stores this information in the <STRONG>cchar_t</STRONG> structure, which is much
105 <STRONG>o</STRONG> It is possible to read a screen dump into a terminal with a differ-
106 ent screen-size, because the library truncates or fills the screen
109 <STRONG>o</STRONG> The ncurses6 <STRONG>getwin</STRONG> reads the legacy screen dumps from ncurses5.
112 </PRE><H3><a name="h3-ncurses5-_legacy_">ncurses5 (legacy)</a></H3><PRE>
113 The screen-dump feature was added to ncurses in June 1995. While there
114 were fixes and improvements in succeeding years, the basic scheme was
117 <STRONG>o</STRONG> The <STRONG>WINDOW</STRONG> structure was written in binary form.
119 <STRONG>o</STRONG> The <STRONG>WINDOW</STRONG> structure refers to lines of data, which were written as
120 an array of binary data following the <STRONG>WINDOW</STRONG>.
122 <STRONG>o</STRONG> When <STRONG>getwin</STRONG> restored the window, it would keep track of offsets
123 into the array of line-data and adjust the <STRONG>WINDOW</STRONG> structure which
124 was read back into memory.
126 This is similar to Unix SystemV, but does not write a "magic number" to
127 identify the file format.
130 </PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
131 There is no standard format for <STRONG>putwin</STRONG>. This section gives a brief
132 description of the existing formats.
135 </PRE><H3><a name="h3-X_Open-Curses">X/Open Curses</a></H3><PRE>
136 Refer to <EM>X/Open</EM> <EM>Curses,</EM> <EM>Issue</EM> <EM>7</EM> (2009).
138 X/Open's documentation for <EM>enhanced</EM> <EM>curses</EM> says only:
140 The <EM>getwin(</EM> <EM>)</EM> function reads window-related data stored in the file
141 by <EM>putwin(</EM> <EM>)</EM>. The function then creates and initializes a new win-
144 The <EM>putwin(</EM> <EM>)</EM> function writes all data associated with <EM>win</EM> into the
145 <EM>stdio</EM> stream to which <EM>filep</EM> points, using an <STRONG>unspecified</STRONG> <STRONG>format</STRONG>.
146 This information can be retrieved later using <EM>getwin(</EM> <EM>)</EM>.
148 In the mid-1990s when the X/Open Curses document was written, there
149 were still systems using older, less capable curses libraries (aside
150 from the BSD curses library which was not relevant to X/Open because it
151 did not meet the criteria for <EM>base</EM> <EM>curses</EM>). The document explained the
152 term "enhanced" as follows:
154 <STRONG>o</STRONG> Shading is used to identify <EM>X/Open</EM> <EM>Enhanced</EM> <EM>Curses</EM> material,
155 relating to interfaces included to provide enhanced capabilities
156 for applications originally written to be compiled on systems
157 based on the UNIX operating system. Therefore, the features
158 described may not be present on systems that conform to <STRONG>XPG4</STRONG> <STRONG>or</STRONG>
159 <STRONG>to</STRONG> <STRONG>earlier</STRONG> <STRONG>XPG</STRONG> <STRONG>releases</STRONG>. The relevant reference pages may pro-
160 vide additional or more specific portability warnings about use
163 In the foregoing, emphasis was added to <STRONG>unspecified</STRONG> <STRONG>format</STRONG> and to <STRONG>XPG4</STRONG>
164 <STRONG>or</STRONG> <STRONG>to</STRONG> <STRONG>earlier</STRONG> <STRONG>XPG</STRONG> <STRONG>releases</STRONG>, for clarity.
167 </PRE><H3><a name="h3-Unix-SystemV">Unix SystemV</a></H3><PRE>
168 Unix SystemV curses identified the file format by writing a "magic num-
169 ber" at the beginning of the dump. The <STRONG>WINDOW</STRONG> data and the lines of
170 text follow, all in binary form.
172 The Solaris curses source has these definitions:
174 /* terminfo magic number */
177 /* curses screen dump magic number */
178 #define SVR2_DUMP_MAGIC_NUMBER 0433
179 #define SVR3_DUMP_MAGIC_NUMBER 0434
181 That is, the feature was likely introduced in SVr2 (1984), and improved
182 in SVr3 (1987). The Solaris curses source has no magic number for SVr4
183 (1989). Other operating systems (AIX and HPUX) use a magic number
184 which would correspond to this definition:
186 /* curses screen dump magic number */
187 #define SVR4_DUMP_MAGIC_NUMBER 0435
189 That octal number in bytes is 001, 035. Because most Unix vendors use
190 big-endian hardware, the magic number is written with the high-order
195 After the magic number, the <STRONG>WINDOW</STRONG> structure and line-data are written
196 in binary format. While the magic number used by the Unix systems can
197 be seen using <STRONG>od(1)</STRONG>, none of the Unix systems documents the format used
200 The Unix systems do not use identical formats. While collecting infor-
201 mation for for this manual page, the <EM>savescreen</EM> test-program produced
202 dumps of different size (all on 64-bit hardware, on 40x80 screens):
204 <STRONG>o</STRONG> AIX (51817 bytes)
206 <STRONG>o</STRONG> HPUX (90093 bytes)
208 <STRONG>o</STRONG> Solaris 10 (13273 bytes)
210 <STRONG>o</STRONG> ncurses5 (12888 bytes)
213 </PRE><H3><a name="h3-Solaris">Solaris</a></H3><PRE>
214 As noted above, Solaris curses has no magic number corresponding to
215 SVr4 curses. This is odd since Solaris was the first operating system
216 to pass the SVr4 guidelines. Solaris has two versions of curses:
218 <STRONG>o</STRONG> The default curses library uses the SVr3 magic number.
220 <STRONG>o</STRONG> There is an alternate curses library in <STRONG>/usr/xpg4</STRONG>. This uses a
221 textual format with no magic number.
223 According to the copyright notice, the <EM>xpg4</EM> Solaris curses library
224 was developed by MKS (Mortice Kern Systems) from 1990 to 1995.
226 Like ncurses6, there is a file-header with parameters. Unlike
227 ncurses6, the contents of the window are written piecemeal, with
228 coordinates and attributes for each chunk of text rather than writ-
229 ing the whole window from top to bottom.
232 </PRE><H3><a name="h3-PDCurses">PDCurses</a></H3><PRE>
233 PDCurses added support for screen dumps in version 2.7 (2005). Like
234 Unix SystemV and ncurses5, it writes the <STRONG>WINDOW</STRONG> structure in binary,
235 but begins the file with its three-byte identifier "PDC", followed by a
236 one-byte version, e.g.,
241 </PRE><H3><a name="h3-NetBSD">NetBSD</a></H3><PRE>
242 As of April 2017, NetBSD curses does not support <STRONG>scr_dump</STRONG> and
243 <STRONG>scr_restore</STRONG> (or <STRONG>scr_init</STRONG>, <STRONG>scr_set</STRONG>), although it has <STRONG>putwin</STRONG> and <STRONG>getwin</STRONG>.
245 Like ncurses5, NetBSD <STRONG>putwin</STRONG> does not identify its dumps with a useful
246 magic number. It writes
248 <STRONG>o</STRONG> the curses shared library major and minor versions as the first two
249 bytes (e.g., 7 and 1),
251 <STRONG>o</STRONG> followed by a binary dump of the <STRONG>WINDOW</STRONG>,
253 <STRONG>o</STRONG> some data for wide-characters referenced by the <STRONG>WINDOW</STRONG> structure,
256 <STRONG>o</STRONG> finally, lines as done by other implementations.
259 </PRE><H2><a name="h2-EXAMPLE">EXAMPLE</a></H2><PRE>
260 Given a simple program which writes text to the screen (and for the
261 sake of example, limiting the screen-size to 10x20):
263 #include <curses.h>
269 putenv("COLUMNS=20");
272 init_pair(1, COLOR_WHITE, COLOR_BLUE);
273 init_pair(2, COLOR_RED, COLOR_BLACK);
274 bkgd(<STRONG>COLOR_PAIR(1)</STRONG>);
280 attrset(A_REVERSE | <STRONG>COLOR_PAIR(2)</STRONG>);
288 When run using ncurses6, the output looks like this:
290 \210\210\210\210ncurses 6.0.20170415
300 _bkgrnd=\{NORMAL|C1}\s
302 1:\{NORMAL|C1}\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s
303 2:\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s
304 3:\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s
305 4:\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s
306 5:\s\s\s\s\s\{BOLD}Hello\{NORMAL}\s\s\s\s\s\s\s\s\s\s
307 6:\s\s\s\s\s\{REVERSE|C2}World!\{NORMAL|C1}\s\s\s\s\s\s\s\s\s
308 7:\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s
309 8:\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s
310 9:\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s
311 10:\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s
313 The first four octal escapes are actually nonprinting characters, while
314 the remainder of the file is printable text. You may notice:
316 <STRONG>o</STRONG> The actual color pair values are not written to the file.
318 <STRONG>o</STRONG> All characters are shown in printable form; spaces are "\s" to
319 ensure they are not overlooked.
321 <STRONG>o</STRONG> Attributes are written in escaped curly braces, e.g., "\{BOLD}",
322 and may include a color-pair (C1 or C2 in this example).
324 <STRONG>o</STRONG> The parameters in the header are written out only if they are
325 nonzero. When reading back, order does not matter.
327 Running the same program with Solaris <EM>xpg4</EM> curses gives this dump:
363 Solaris <STRONG>getwin</STRONG> requires that all parameters are present, and in the
364 same order. The <EM>xpg4</EM> curses library does not know about the <STRONG>bce</STRONG> (back
365 color erase) capability, and does not color the window background.
367 On the other hand, the SVr4 curses library does know about the back-
368 ground color. However, its screen dumps are in binary. Here is the
369 corresponding dump (using "od -t x1"):
371 0000000 1c 01 c3 d6 f3 58 05 00 0b 00 0a 00 14 00 00 00
372 0000020 00 00 02 00 00 00 00 00 00 00 00 00 00 00 00 00
373 0000040 00 00 b8 1a 06 08 cc 1a 06 08 00 00 09 00 10 00
374 0000060 00 00 00 80 00 00 20 00 00 00 ff ff ff ff 00 00
375 0000100 ff ff ff ff 00 00 00 00 20 80 00 00 20 80 00 00
376 0000120 20 80 00 00 20 80 00 00 20 80 00 00 20 80 00 00
378 0000620 20 80 00 00 20 80 00 00 20 80 00 00 48 80 00 04
379 0000640 65 80 00 04 6c 80 00 04 6c 80 00 04 6f 80 00 04
380 0000660 20 80 00 00 20 80 00 00 20 80 00 00 20 80 00 00
382 0000740 20 80 00 00 20 80 00 00 20 80 00 00 57 00 81 00
383 0000760 6f 00 81 00 72 00 81 00 6c 00 81 00 64 00 81 00
384 0001000 21 00 81 00 20 80 00 00 20 80 00 00 20 80 00 00
385 0001020 20 80 00 00 20 80 00 00 20 80 00 00 20 80 00 00
387 0001540 20 80 00 00 20 80 00 00 00 00 f6 d1 01 00 f6 d1
388 0001560 08 00 00 00 40 00 00 00 00 00 00 00 00 00 00 07
389 0001600 00 04 00 01 00 01 00 00 00 01 00 00 00 00 00 00
390 0001620 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
395 </PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
396 <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>.
399 </PRE><H2><a name="h2-AUTHORS">AUTHORS</a></H2><PRE>
401 extended screen-dump format for ncurses 6.0 (2015)
404 screen dump feature in ncurses 1.9.2d (1995)
408 <STRONG><A HREF="scr_dump.5.html">scr_dump(5)</A></STRONG>
412 <li><a href="#h2-NAME">NAME</a></li>
413 <li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
414 <li><a href="#h2-DESCRIPTION">DESCRIPTION</a>
416 <li><a href="#h3-ncurses6">ncurses6</a></li>
417 <li><a href="#h3-ncurses5-_legacy_">ncurses5 (legacy)</a></li>
420 <li><a href="#h2-PORTABILITY">PORTABILITY</a>
422 <li><a href="#h3-X_Open-Curses">X/Open Curses</a></li>
423 <li><a href="#h3-Unix-SystemV">Unix SystemV</a></li>
424 <li><a href="#h3-Solaris">Solaris</a></li>
425 <li><a href="#h3-PDCurses">PDCurses</a></li>
426 <li><a href="#h3-NetBSD">NetBSD</a></li>
429 <li><a href="#h2-EXAMPLE">EXAMPLE</a></li>
430 <li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>
431 <li><a href="#h2-AUTHORS">AUTHORS</a></li>