How can I use Vim as a hex editor? [duplicate]

Question

Is there a neat way I can view binary files as hex in Vim, and save it back to binary from the hex?

Answer 1

You can use the xxd command to transform a file in Vim to hex representation, doing

:%!xxd

: enters command-line mode, % matches whole file as a range, ! filters that range through an external command, xxd is that external shell command

Giving an output like this, this is split into octet count/line (octets per line may be changed with parameter -c on xxd command), hex representation, and text representation:

0000000: 5468 6973 2069 7320 6120 7465 7374 0a41  This is a test.A
0000010: 6e6f 7468 6572 206c 696e 650a 416e 6420  nother line.And 
0000020: 7965 7420 616e 6f74 6865 720a            yet another.

Once you make the changes (in the hex part), you can go back to text with -r command on xxd, so

:%!xxd -r

This is a little rudimentary, though I like it in its simplicity and to keep in mind xxd, which is an interesting command line tool (I don't have to do a lot of work on hex, though). You can use some recipes to handle this transformation in a more automatic way like the one described in Improved hex editing.

Answer 2

Taken from :h hex-editing:

If one has a particular extension that one uses for binary files (such as exe,
bin, etc), you may find it helpful to automate the process with the following
bit of autocmds for your <.vimrc>.  Change that "*.bin" to whatever
comma-separated list of extension(s) you find yourself wanting to edit:

" vim -b : edit binary using xxd-format!
augroup Binary
  au!
  au BufReadPre  *.bin let &bin=1
  au BufReadPost *.bin if &bin | %!xxd
  au BufReadPost *.bin set ft=xxd | endif
  au BufWritePre *.bin if &bin | %!xxd -r
  au BufWritePre *.bin endif
  au BufWritePost *.bin if &bin | %!xxd
  au BufWritePost *.bin set nomod | endif
augroup END

You may want to look at: How do I navigate to topics in Vim's documentation?