I knew that we can hex edit a file with vi/vim, using the command %!xxd (call *nix hex dump) and %!xxd -r (exit *nix hex dump).
The problem is, if I do some hex-editing in the hex-code area, there is no corresponding cursor displayed in the ascii-code area, and vice-versa.
In contrast, when the file is edited with ghex, there are two cursors, one is with the current edit operation, the other shows the corresponding position in the other panel.
For example, if a text file contains a letter 'f', and I am using ghex to edit it, the cursor in the right panel will show the current character to be edit is 'f', when I move the cursor to the hex value 0x66 in the left panel.
Does this feature already exist in vi/vim/xxd, but I haven't found out?
Just so we're clear, xxd is not a vim command; it is an external program that translates to/from hex dumps. The command %!xxd means 'run the external program xxd, passing it the contents of this file via stdin, and replace the contents of the file with the result.'
From that, I hope you understand that you are not using some special mode of vim to edit these hex dumps. The hex dump is simply the text you see, and you are editing it as a normal text file.
There may be some extension to vim which provides the functionality you are looking for (I haven't looked very hard), but in answer to your question, there is no built-in functionality to do this.
Related
This question already has answers here:
What does the ^M character mean in Vim?
(15 answers)
Closed 2 years ago.
I'm new to Linux sorry if my question sounds dumb.
We know that Linux and Mac OS X use \n (0xa), which is the ASCII line feed (LF) character. MS Windows and Internet protocols such as HTTP use the sequence \r\n (0xd 0xa). If you create a file foo.txt in Windows and then view it in a Linux text editor, you’ll see an annoying ^M at the end of each line, which is how Linux tools display the CR character.
Bu why Linux tools display the CR character as ^M? as my understanding is, \r (carriage return) is to move the cursor in the beginning of the current line, so the sensible approach to display it is like, when you open the file, you see the cursor is in the beginning of the line(that contains \r), so ^M shouldn't be displayed?
PS: some people post answers that how to remove ^M, but I wnat to know why eventually^M is displayed rather than moving the cursor in the beginning, which is the definition of carriage return.
The ASCII control characters like TAB, CR, NL and others are intended to control the printing position of a teletypewriter-like display device.
A text editor isn't such a device. It is not appropriate for a text editor to treat a CR character literally as meaning "go to the first column"; it would make a confusing gibberish out of the editing experience.
A text editor works by parsing a text file's representation, to create an internal representation which is presented to the user. On Unix-like operating systems, a file is represented by zero or more lines, which are terminated by the ASCII NL character. Any CR characters that occur just look like part of the data, and not part of the line separation.
Not all editors behave the same way. For instance, the Vim editor will detect that a file uses CR-LF line endings, and load it properly using that representation. A flag is set for that buffer which indicates that it's a "DOS" file, so that when you save it, the same representation is reproduced.
That said, there is a feature in the actual Linux kernel for representing control characters like CR using the ^M notation. The TTY line discipline for any given TTY device can be configured to print characters in this notation, but only when echoing back the characters received.
Demo:
$ stty echoctl # turn on notational echo of control characters
$ cat # run some non-interactive program with rudimentary line input
^F^F^F^F^F^F
^C
$
Above, the Ctrl-F that I entered was echoed back as ^F. So, in fact there is a "Linux editor" which uses this notation: the rudimentary line editor of the "canonical input mode" line discipline.
I've been tinkering with multiple hex editors but nothing really has worked.
What I'm looking for is a way to change a binary in actual binary (not in hex). This is purely for educational purposes and I know it's trivial to convert between both, but I wanted to be able to change the ones and zeroes just like I would do hex.
I've tried using vim with the %!xxd -b but then it won't work with %!xxd -r. I know how to convert the file into binary, but I'm looking for a way to dynamically change it in this format and being able to save it.
Better yet would be if I could find a way to actually create a binary by coding purely in actual binary.
Any help would be appreciated :D
vim or gvim should work for you directly, without the xxd filter.
Open the file in (g)vim. Place your cursor on a character and type ga to see its character code in the status line. To insert character NNN, place your cursor where you want it, go in insert mode and type Ctrl-v and then the three digit decimal code value. Use Ctrl-v x HH to enter the character by its hexadecimal code.
Make sure your terminal is not set to use UTF8, because in UTF8, typing Ctrl-v 128 will in fact insert c280, the utf-8 encoding of character 128, instead of 80.
LC_ALL=C vim binary-file
is the easiest way to make sure you're doing binary character based editing in vim, but that might do weird things if your terminal is utf-8.
LC_ALL=C gvim binary-file
should open a stand-alone window with proper display.
FYI, if you did want to work in utf-8, Ctrl-v u HHHH is how to enter the Unicode character with Hex code point HHHH.
windows
open cmd.exe or notepad++ or whatever editor
enable numlock key
On laptops you need to use the function key or the blue / grey silver numbers above alphabet keys (using the numbers on the top line will not work as they map to different scan code.
press alt key + 255 will correspond to 0xff
press alt key + 254 will correspond to 0xfe
see below for a demo
C:\>copy con rawbin.bin
■²ⁿ√·∙⌂~}─^Z
^Z
1 file(s) copied.
C:\>xxd rawbin.bin
0000000: fffe fdfc fbfa f97f 7e7d c41a 0d0a ........~}....
C:\>
I have written some c code, and the end of my output is '\n', when I check the output text file in vim, I cannot find the last empty line, however, when I open it with another text viewer, I can find the last empty line. How can I configure my vim to show the empty line?
The way Vim shows \n / 0x0a at the end of the file is that it opens the file without complaining about [noeol] when :editing the file (in a kind of "reverse logic" from what you expect). Vim's (and Unix) philosophy is that the trailing newline should be there. This can be confusing when one is used to other editors or predominantly works on MS Windows.
There's a lot of discussion and questions about this (e.g. here); as this is unlikely to change, get used to it.
As in subject.
I'd like to fill in a part of the binary file (base address + offset) in vim with a value given.
For example I'd like to add 1M values of 0xfd starting from address 0x0fff.
What command could I use?
Open the file in binary mode, either via vim -b {filespec} or via :edit ++bin {filespec}.
Go to byte index 0x0fff with the go command or :goto. You need to convert to decimal, e.g.: :exe 'goto' 0x0fff.
Insert the value; you can supply a [count] to the i command, and insert arbitrary hex values via :help i_CTRL-V_digit: 1048576i<C-V>xfd<Esc>
Write the file and exit :wq.
An alternative within Vim is using an intermediate hex dump format and converting back and forth via the xxd tool that ships with Vim. See Improved hex editing for details.
So, while Vim isn't the perfect tool for this (as mentioned in the comments, a hex editor is the right / better tool), it can be done.
Is there a way to make cat, less etc. print tab characters instead of tabs being converted to spaces? I am annoyed by this when I copy code from the terminal to an editor.
I am seeing two problems here.
First, destination editor can covert TAB to number of spaces. Some
editor has default feature to convert TAB to number of spaces. If
you disable this feature TAB character you copied from terminal will
be copied as TAB(instead of space) to an editor.
Windows Notepad++ has similar feature
. If you are using vim, this page will be helpful for
vim tab and space conversion
Another, source file in your case terminal may be representing tab
as spaces, please check that first. You can use cat -t filename to
see if you have any TAB in source file or not. That command will
display TAB character as ^I.
It seems this is not possible with less (see answer to the same question on unix.stackexchange).
As a workaround, it works with cat or, for some minimal paging capabilities, with the more command.