Ubuntu Manpage: dhex — hex editor with a diff mode

NAME

     dhex — hex editor with a diff mode

SYNOPSIS

     dhex [-h] [-v] [-g] [-k] [-ab -ad -ah -ao base address] [-f config-file] [-m marker-file]
          [-ob -od -oh -oo offset] [-r searchlog] [-sa -sab string (ascii)]
          [-sh -shb string (hex)] [-w searchlog] [file]
     dhex [-h] [-v] [-g] [-k] [-a1b -a1d -a1h -a1o base address 1]
          [-a2b -a2d -a2h -a2o base address 2] [-cb] [-cd upper-limit] [-cl] [-f config-file]
          [-m marker-file] [-o1b -o1d -o1h -o1o offset1] [-o2b -o2d -o2h -o2o offset2]
          [-r1 searchlog1] [-r2 searchlog2] [-s1a -s1ab -s1h -s1hb string (ascii/hex)]
          [-s2a -s2ab -s2h -s2hb string (ascii/hex)] [-w1 searchlog1] [-w2 searchlog2]
          [file1 file2]

DESCRIPTION

     dhex is a hex editor. It can be used to alter individual bytes in large files. Since it is a
     text-mode program based on ncurses, it can run in numerous scenarios.  Its special feature
     is the diff mode: With it, the user has a visual tool for file comparison. This mode is
     invoked when dhex is called with two instead of one file as parameters.

OPTIONS

All the options are case-insensitive and can be given as either upper- or lowercase
characters.

-ab -ad -ah -ao base address
After loading a file, every address gets a base address other than 0. With this,
it is easier to work on partial memory dumps. The base address can be given as a
binary one with [-ab] , as a decimal one with [-ad] , as a hexadecimal one with
[-ah] or an octal with [-ao].

-a1b -a1d -a1h -a1o base address 1

-a2b -a2d -a2h -a2o base address 2
For the diff mode, it is possible to set two different base addresses. Again, a
binary address can be given as [-a1b -a2b] , as decimal one with [-a1d -a2d] ,
as hexadecimal one with [-a1h -a2h] or an octal one with [-a1o -a2o].

This base address is calculated into the marker files as well as the searchlogs.

-cb -cl Diff mode only: The input files can be correlated from the command line with the
best -cb or longest -cl match. This is very slow.

-cd upper-limit
Diff mode only: The input files can be correlated from the command line with the
minimum difference. To improve the correlation speed, an upper limit can be
provided.

-f configfile
Usually, .dhexrc is being read from the invoker's home directory. With this
parameter, any other config file can be loaded. See dhexrc(5) for a description
of its file format.

-g Shows the license

-h Shows the help screen

-k Starts the keyboard setup manually before any file is being loaded. This is very
helpful when calling dhex from an exotic terminal.

-m markerfile
It is possible in dhex to set bookmarks and store them in a markerfile for later
use. With this parameter, the markerfile is being read at start time, making it
unnecesarry to read them later through the gui. Their file format is described
in dhex_markers(5).

-ob -od -oh -oo offset
After loading a file, the cursor is set to 0, and the first page of bytes is
being shown on the screen. With one of those parameters it is possible to start
at any other location in the file. The cursorposition could be given as a binary
number with [-ob] , as a decimal one with [-od] , as a hexadecimal one with
[-oh] or an octal with [-oo].

-o1b -o1d -o1h -o1o offset1

-o2b -o2d -o2h -o2o offset2
For the diff mode, it is possible to set two different cursorpositions at start
time. Again, the cursorpositions can be given as a binary number with [-o1b
-o2b] , as decimal one with [-o1d -o2d] , as hexadecimal one with [-o1h -o2h] or
an octal one with [-o1o -o2o].

This way, the first few bytes in a file can be skipped, and just the rest can be
compared.

-r searchlog
When searching from the command line, the offsets are being read from this
searchlog. Its format is being decribed in dhex_searchlog(5).

-r1 searchlog1

-r2 searchlog2
When searching in two files simultanously, the offsets can be read from two
different searchlogs.

-sa -sab -sh -shb string
Instead of setting the cursor offset to an absolute value, it is possible to
search for a specific string from the command line. If there is an additional
[-ob -od -oh -oo offset] present, the search will start there. It is possible to
read and write search logs with [-r searchlog] and [-w searchlog] respectively.
With [-sa string] is being interpreted as ASCII. [-sh string] interprets it as
hex. For backwards search, [-sab string] or [-shb string] can be applied.

-s1a -s1ab -s1h -s1hb string1

-s2a -s2ab -s2h -s2hb string2
In the diff mode, it is possible to search for two strings in two files
simultanously.

-v Prints out the version of dhex.

-w searchlog
When searching from the command line, write the results into this searchlog and
quit. It is being written in the format described in dhex_searchlog(5.)

-w1 searchlog1

-w2 searchlog2
When searching in two files simultanously, write the results from both searches
into those log files.

USER INTERFACE

General
Menus have hotkeys, they are being presented in a different color. To jump from one menu
item to the next, the cursor keys or the TAB key can be used.

Input fields can be closed by pressing ESC, ENTER, or any cursor key. Only pressing ESC will
not save the changes made in there.

The keyboard setup
When running dhex for the first time, without any configfile present, or with the parameter
-k, the first screen shown is that of the keyboard setup. In this screen, the program asks
the user to press certain keys. Which are (in order) ESCAPE, F1, F2, F3, F4, F5, F6, F7, F8,
F9, F10, BACKSPACE, DEL, ENTER, TAB, UP, DOWN, RIGHT, LEFT, PG UP, PG DOWN, HOME, END. It
also tells the user what it intends to do with those keys later. So the user can decide on
any alternative he chooses. If he does not want to bind a specific function to a certain
key, he can simply press ESCAPE and skip to the next question.

After pressing all the keys, the user can chose whether or not to write those keys into the
config file.

The main screen
The main screen is broken down into three columns: The first column contains the offset
within the file for the current line. The second column contains the bytes in the file in
hex format. Finally, the third coumn contains the same bytes, but this time in ascii format.
If a byte is not printable, it is being substituted with a '.'. How many bytes are are
being shown in a line depends on the width of the terminal. For example, if the terminal is
80 characters wide, 16 bytes are being shown in each line.

If no other [-o] or [-a] parameter was given at start time, the cursor is being set to
offset 0. It is also being shown in the hex column. Here, it can be moved with the cursor
keys. When entering a hexadecimal number, the file is being edited. The file can be edited
in the ascii column as well, simply by pressing the TAB key (or whichever key was
substituted for it in the keyboard setup). Pressing TAB again will return the cursor to the
hex column. Pressing F9 (or its substitute) will undo the last of the changes. Changes are
being shown in a differnt color.

Editing is not possible in the diff mode. Here, pressing the cursor keys will move both
files synchronously.

The goto screen
Pressing F1 (or its substitute) will open the Goto... screen. Here, it is possible to jump
to a specific address directly, without the need of scrolling there with the cursor keys.
The address can be entered in the 'To' field, either absolute or relative (to leap over a
specified amount of bytes). An absolute address is being chosen by pressing '=', and a
relative one by pressing '+' or '-', for a positive or negative leap respectively.
Regardless of the adressing mode, it has to be entered as a hexadecimal number.

It is also possible to set up to ten bookmarks in this screen: Pressing '0'...'9' will
select one of them. Moving the cursor to "Set" and pressing ENTER will alter one of those
book marks. The "Diff:" fields are showing the difference between the actual cursor position
and the bookmark.

Bookmarks can be stored and loaded, for this there are the "Save Markers" and "Load Markers"
items on the bottom. Upon selecting one of them, the user is being prompted for a filename.
It is possible to load a marker file at start time, by providing the [-m markerfile]
parameter. dhex_markers(5) describes the format of the marker files.

Searching
Pressing F2 (or its subsitute) will open the Search... screen. Here, a short string can be
entered (either in hex, or in ascii). If no logfiles are being selected, the cursor will
jump to the next occurance of this search string upon selection of "Go". It can be chosen if
the search is supposed to be conducted forward of backwards.

To jump to the next occurance, F3 (or its substitute) has to be pressed. To jump to the
previous one, F4 has to be pressed. The search itself wraps at the edges of the file,
meaning that when it reaches the end, it will start from the beginning and vice versa.

Searchlogs are an advanced way of searching: Writing to the searchlog does not jump the
cursor from one occurance to the next. Instead, it will write the offsets of all of them
into the logfile. Their format is described in dhex_searchlog(5).

Reading from this searchlog means that the search does not cover the whole file: Only the
addresses which have been provided in this file are being searched. Thus it is possible to
search for specific changes. Like for example the number of lives stored in the save file of
a game. dhex_searchlog(5) describes the format of the searchlog.

HexCal
Pressing F5 (or its substitute) will open a small 64 bit calculator. This calculator is
capable of not only performing arithmetic operations (+, -, *, /, modulo), but also logic
ones. (and, or, xor, shift). There are three columns to enter numbers as hexadecimals,
decimals or in binary format. Pressing 'x' will close this screen.

Correlation
When dhex(1) is running in diff mode, pressing F6 (or its substitute) will open the dialog
for file correlation. This will try to find the optimal offset between the two files. There
are three algorithms available for finding this offset: Searching for the best match (as
many bytes as possible are the same), the longest match (as many consecutive bytes match as
possible), or the minimum difference (as little differences between the bytes as possible).

Even though it seems like the same at first, looking for the minimum difference is in fact
faster. This can be improved even more, if the user sets an upper difference limit.

Upon selecting Go, the program will search for the optimal offset. This will take some time.

Saving and quitting
Pressing F10 (or its substitute) will close dhex. In case there have been changes made to
the file, a save dialog opens up. Here, it is possible to select whether or not to write the
changes back into the file.

FILES

     $HOME/.dhexrc: The default location of the config file. If the $HOME-variable is not set,
     its location has to be provided manually.

BUGS

     Report bugs to <dettus@dettus.net>.  Make sure to include DHEX somewhere in the subject.

AUTHOR

     Written by Thomas Dettbarn