The curses library provides applications with the ability to write the
contents of a window to an external file using scr_dump or putwin, and
@@ -129,48 +125,34 @@
- There is no standard format for putwin. This section gives a brief
- description of the existing formats.
+ There is no standard format for curses screen dumps. A brief survey of
+ the existing implementations follows.
- Refer to X/OpenCurses,Issue7 (2009).
-
- X/Open's documentation for enhancedcurses says only:
+ X/Open Curses, Issue 7 specifies little. It says (boldface emphasis
+ added)
- The getwin() function reads window-related data stored in the file
- by putwin(). The function then creates and initializes a new
+ "[t]he getwin() function reads window-related data stored in the
+ file by putwin(). The function then creates and initializes a new
window using that data.
- The putwin() function writes all data associated with win into the
- stdio(3) stream to which filep points, using an unspecifiedformat.
- This information can be retrieved later using getwin().
-
- In the mid-1990s when the X/Open Curses document was written, there
- were still systems using older, less capable curses libraries (aside
- from the BSD curses library which was not relevant to X/Open because it
- did not meet the criteria for basecurses). The document explained the
- term "enhanced" as follows:
-
- o Shading is used to identify X/OpenEnhancedCurses material,
- relating to interfaces included to provide enhanced capabilities
- for applications originally written to be compiled on systems
- based on the Unix operating system. Therefore, the features
- described may not be present on systems that conform to XPG4or
- toearlierXPGreleases. The relevant reference pages may
- provide additional or more specific portability warnings about
- use of the material.
+ The putwin() function writes all data associated with win into the
+ stdio stream to which filep points, using an unspecifiedformat.
+ This information can be retrieved later using getwin()."
- In the foregoing, emphasis was added to unspecifiedformat and to XPG4
- ortoearlierXPGreleases, for clarity.
+ In the mid-1990s when the X/Open Curses document was written, there
+ were still System V systems using older, less capable curses libraries.
+ BSD curses was not relevant to X/Open because it did not meet the
+ criteria for base-level conformance; see ncurses(3x).
-
- Unix System V curses identified the file format by writing a "magic
- number" at the beginning of the dump. The WINDOW data and the lines of
- text follow, all in binary form.
+
+ System V curses identified the file format by writing a "magic number"
+ at the beginning of the dump. The WINDOW data and the lines of text
+ follow, all in binary form.
- The Solaris curses source has these definitions:
+ Solaris curses has the following definitions.
/* terminfo magic number */
#define MAGNUM 0432
@@ -180,28 +162,28 @@
#define SVR3_DUMP_MAGIC_NUMBER 0434
That is, the feature was likely introduced in SVr2 (1984), and improved
- in SVr3 (1987). The Solaris curses source has no magic number for SVr4
- (1989). Other operating systems (AIX and HP-UX) use a magic number
- which would correspond to this definition:
+ in SVr3 (1987). Solaris curses 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 use
- big-endian hardware, the magic number is written with the high-order
- byte first, e.g.,
+ 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 WINDOW structure and line-data are written
- in binary format. While the magic number used by the Unix systems can
- be seen using od(1), none of the Unix systems documents the format used
- for screen-dumps.
+ After the magic number, the WINDOW structure and line data are written
+ in binary format. While the magic number used by these systems can be
+ observed with od(1), none of them documents the format used for screen
+ dumps.
- The Unix systems do not use identical formats. While collecting
- information for for this manual page, the savescreen test-program
- produced dumps of different size (all on 64-bit hardware, on 40x80
- screens):
+ Nor do they use an identical format, even with the System V family.
+ The ncursessavescreen 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):
o AIX (51817 bytes)
@@ -213,53 +195,54 @@
- As noted above, Solaris curses has no magic number corresponding to
- SVr4 curses. This is odd since Solaris was the first operating system
- to pass the SVr4 guidelines. Solaris has two versions of curses:
+ As noted above, Solaris curses has no magic number corresponding to
+ SVr4 curses. This is odd, since Solaris was the first operating system
+ to meet the SVr4 guidelines. Solaris furthermore supplies two versions
+ of curses.
- o The default curses library uses the SVr3 magic number.
+ o The default curses library uses the SVr3 magic number.
- o There is an alternate curses library in /usr/xpg4. This uses a
- textual format with no magic number.
+ o An alternate curses library (which we term xcurses), available in
+ /usr/xpg4, uses a textual format with no magic number.
- According to the copyright notice, the xpg4 Solaris curses library
- was developed by MKS (Mortice Kern Systems) from 1990 to 1995.
+ According to its copyright notice, this xcurses library was
+ developed by MKS (Mortice Kern Systems) from 1990 to 1995.
- Like ncurses6, there is a file-header with parameters. Unlike
- ncurses6, the contents of the window are written piecemeal, with
- coordinates and attributes for each chunk of text rather than
+ 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.
- PDCurses added support for screen dumps in version 2.7 (2005). Like
- Unix System V and ncurses5, it writes the WINDOW structure in binary,
- but begins the file with its three-byte identifier "PDC", followed by a
- one-byte version, e.g.,
+ PDCurses added support for screen dumps in version 2.7 (2005). Like
+ System V and ncurses5, it writes the WINDOW structure in binary, but
+ begins the file with its three-byte identifier "PDC", followed by a
+ single-byte version number.
"PDC\001"
- As of April 2017, NetBSD curses does not support scr_dump and
+ As of April 2017, NetBSD curses does not support scr_dump and
scr_restore (or scr_init, scr_set), although it has putwin and getwin.
- Like ncurses5, NetBSD putwin does not identify its dumps with a useful
+ Like ncurses5, NetBSD putwin does not identify its dumps with a useful
magic number. It writes
- o the curses shared library major and minor versions as the first two
- bytes (e.g., 7 and 1),
+ o the curses shared library major and minor versions as the first two
+ bytes (for example, 7 and 1),
o followed by a binary dump of the WINDOW,
- o some data for wide-characters referenced by the WINDOW structure,
+ o some data for wide characters referenced by the WINDOW structure,
and
o finally, lines as done by other implementations.
- Given a simple program which writes text to the screen (and for the
+ 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>
@@ -317,13 +300,13 @@
o The actual color pair values are not written to the file.
- o All characters are shown in printable form; spaces are "\s" to
+ o All characters are shown in printable form; spaces are "\s" to
ensure they are not overlooked.
- o Attributes are written in escaped curly braces, e.g., "\{BOLD}",
+ o Attributes are written in escaped curly braces, e.g., "\{BOLD}",
and may include a color pair (C1 or C2 in this example).
- o The parameters in the header are written out only if they are
+ o 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 xpg4 curses gives this dump:
@@ -362,12 +345,12 @@
9,19,0,0,
CUR=11,5
- Solaris getwin requires that all parameters are present, and in the
- same order. The xpg4 curses library does not know about the bce (back
+ Solaris getwin requires that all parameters are present, and in the
+ same order. The xpg4 curses library does not know about the bce (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
+ 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
@@ -407,12 +390,11 @@
-ncurses 6.4 2023-12-23 scr_dump(5)
+ncurses 6.4 2023-12-30 scr_dump(5)