jakhex

jakhex is a curses based full screen hex editor.

It supports the following features:

• curses based full screen interface hex editor
• POSIX C99 with a single dependency on a curses library
• ability to truncate or extend files, including inserting bytes in the middle
• read a file and insert it in the buffer at an arbitrary position
• cursor based navigation
• jump to absolute addresses
• jump to relative offsets from the current cursor position
• shows interpretation of the next few bytes as ints, floats and string with both big- and little endianness
• shows a binary stream starting at the current cursor location
• punch in (overwrite) data in hex, ASCII, or full int- and floating point numbers with either big- or little endianness
• 26 address registers you can use to save your favourite locations
• region based delete, copy, insert and overwrite commands using a single clipboard buffer
• efficiently search both forward and backwards for an arbitrary binary string, typed in either in hex or ASCII
• ability to edit large files, to the extent of your patience and RAM. I've successfully edited files slightly larger than 4GiB.

It has the following limitations:

• its in-memory buffer is stored as a big contiugous array
  • meaning, loading files implies trying to allocate that much memory
  • you can derive from that what kind of file sizes you can load at any time
• the screen width is fixed to 80 columns, 32 bytes per line
  • other hex editors annoy me in that I need to fiddle with the screen size to get the line width to align with a round number that's easy to do maths with
  • only the bottom 32bits of addresses are printed in the first column, because I ran out of screen space
• searching doesn't remember what you previously searched for (but you can use tmux's/X11's kill buffer to repeatedly paste the same search string)
• the details pane can't be hidden, so you need at least 13 lines of screen
• searching doesn't support patterns nor regular expressions
• region commands always prompt you for a pair of markers
• keys are not rebindable, and the bindings are brain dead. Be sure to print out a cheat sheet!
• single buffer only
• any file related commands update the "last mentioned file name" which may not be what you want
• markers are not relocated if you insert bytes before their current address (they hold a number which can be used as an absolute address)
• ASCII only; I imagine you're here mostly to look at bits and bytes, possibly to diagnose why you have invalid UTF-8 at address 0x145f2200. The only issue is with filenames containing non-ASCII or non-printable characters; you can symlink your file to ~/link to work around this.
• there are no preferences and no rc files
• while the g, + and - commands accept both dec and hex input, the command line invocation only accepts decimal input
• string search limits you to a 2^31-2 long needle, but I hope that doesn't bother you. I haven't actually tested with anything longer than what you can type off the top of your head, so it's more of a theoretical limit

You can edit a file and jump to offset 0xA000 with

jakhex file +40960

See jakhex -h or man ./jakhex.1 for more information.

Why does this exist?

Easy: I didn't have a full featured hex editor that was relatively easy and pain free to set up and use. So I wrote my own that does all the stuff I need.

Building

This project depends on some curses library, e.g. ncurses, installed as a system library and system headers.

The code is (or should be) conformant to C99 and POSIX, so all you need is a C99 compiler on a POSIX compatible system. I've only tested on Alpine and RHEL at the time of writing.

Run

make
make install

Changes

1.0.5 -> 1.0.6

Fix memory leak related to saved search strings.

1.0.4 -> 1.0.5

• add support for negative offsets in command line invocation and in g command

1.0.3 -> 1.0.4

• repeat search
• fix compiler warnings
• fix cancelling out of "Which marker?" prompts
• fix punch in which would blank out a byte when trying to cancel out of the prompt
• "ESC" is a valid key for "NO" given a yes/no question
• backward searches start from the left of the cursor position; reverse searches that would include the cursor position will no longer match there; this is because it was impossible to search backwards for a single byte; well, it could have been fixed differently, but that's too much work

1.0.1 -> 1.0.3

• fix bug where the window would scroll too late once hitting the separator

1.0.0 -> 1.0.1

• Fix bug in x (kill region) command which would cause a hang / crash
• man page tweaks
• fix warnings reported by gcc -Wall
• update Makefile to compile with -O2 by default
• update README
• add ^G in normal mode to report file size in a better human readable way
• change reverse search to include the byte you are currently on; this is annoying for single byte reverse searches, but it is what you actually want for multibyte reverse searches; forward search is unaffected.
• fix display or ridiculously large files; the buffer contents were correct, the display wasn't
• fix bug inserting bytes in files larger than 4GB