This tip shows how to convert numbers from hexadecimal to decimal, and the reverse. A variety of methods are given, including some simple commands you can enter, and some scripts to easily replace hex numbers with decimal, or to replace decimal with hex. Handling percent-encoded text is also discussed, and there are links to tips showing how to edit a binary file in hex.
Commands[]
Occasional conversions can be performed by entering commands. In Vim, put the cursor on 0x12345 and type :echo
then Space Ctrl-R Ctrl-W Enter. That will execute :echo 0x12345
which displays 74565 (decimal equivalent of hex 12345).
An example of converting decimal to hex would be to enter :echo printf('%x',74565)
which displays 12345 (hex equivalent of decimal 74565).
In addition, the expression register can be used to enter converted numbers while typing. In insert mode, press Ctrl-R then =
then the expression wanted, then press Enter. The value of the expression is inserted, and you will remain in insert mode. For example, <C-R>=0x09ab<Enter>
will insert 2475
, and <C-R>=printf('0x%04x',2475)<Enter>
will insert 0x09ab
.
In normal mode, type ga
to display the decimal and hex values for the character under the cursor, or type g8
to display the hex bytes for a UTF-8 character.
The following commands illustrate other simple techniques to convert strings to numbers which are displayed in decimal (the :echo
is just for illustration; these techniques would be used in a script). The first shows that adding zero to a string converts the string to a number.
Command | Output | Description |
---|---|---|
:echo '0012' + 0 |
10 | octal 12 due to leading zero |
:echo str2nr('0012') |
12 | decimal 12 (leading zeros ignored) |
:echo str2nr('0x0a2f', 16) |
2607 | hex a2f |
:echo str2nr('0a2f', 16) |
2607 | same ('0x' not required with base 16) |
:echo str2nr('^R^W', 16) |
(decimal) | hex word under cursor (press Ctrl-R Ctrl-W) |
The following convert decimal numbers to hex strings.
Command | Output | Description |
---|---|---|
:echo printf('%x', 1234) |
4d2 | decimal 1234 in hex |
:echo printf('%04x', 1234) |
04d2 | same, with leading zeros to four digits |
:echo printf('%x', ^R^W) |
(hex) | decimal word under cursor (press Ctrl-R Ctrl-W) |
Copying a hex number as decimal[]
With the following mapping, you can put the cursor on a hex number and press \h
(assuming the default backslash leader) to yank the value of the hex number (using :let
means the equivalent decimal string is copied). You can then move the cursor elsewhere and press p
to paste the decimal value.
nnoremap \h :let @@=<C-R><C-W><CR>
Alternatively, you can use a global variable to avoid using a register. With these mappings, \h
will yank a hex value, and \p
will paste the decimal string:
nnoremap \h :let Value=<C-R><C-W><CR> nnoremap \p :if exists('Value')<Bar>normal i<C-R>=Value<CR><Esc><Bar>:endif<CR>
User commands[]
Put the following in your vimrc to define user commands to convert between hex and decimal. You can convert a number entered on the command line, or all numbers in selected text.
command! -nargs=? -range Dec2hex call s:Dec2hex(<line1>, <line2>, '<args>') function! s:Dec2hex(line1, line2, arg) range if empty(a:arg) if histget(':', -1) =~# "^'<,'>" && visualmode() !=# 'V' let cmd = 's/\%V\<\d\+\>/\=printf("0x%x",submatch(0)+0)/g' else let cmd = 's/\<\d\+\>/\=printf("0x%x",submatch(0)+0)/g' endif try execute a:line1 . ',' . a:line2 . cmd catch echo 'Error: No decimal number found' endtry else echo printf('%x', a:arg + 0) endif endfunction command! -nargs=? -range Hex2dec call s:Hex2dec(<line1>, <line2>, '<args>') function! s:Hex2dec(line1, line2, arg) range if empty(a:arg) if histget(':', -1) =~# "^'<,'>" && visualmode() !=# 'V' let cmd = 's/\%V0x\x\+/\=submatch(0)+0/g' else let cmd = 's/0x\x\+/\=submatch(0)+0/g' endif try execute a:line1 . ',' . a:line2 . cmd catch echo 'Error: No hex number starting "0x" found' endtry else echo (a:arg =~? '^0x') ? a:arg + 0 : ('0x'.a:arg) + 0 endif endfunction
The above defines user commands :Dec2hex
and :Hex2dec
that will either display the result of converting a number that you enter, or will convert all numbers in selected text. A decimal number is a word consisting only of decimal digits, while a hex number consists of "0x" followed by one or more hex digits.
If no argument is entered with these commands, a range may be specified. The default range is the current line. A visual selection (character, line, or block) can also specify a range. When using a visual block (selection starts with Ctrl-V, or Ctrl-Q if Ctrl-V is used for paste), only numbers inside the block are converted. Example commands:
Command | Description |
---|---|
:Dec2hex 496 |
Displays 1f0 (hex equivalent of decimal 496). |
:Dec2hex |
Converts all decimal numbers to hex in current line. |
:'<,'>Dec2hex |
Same, for all visually selected text (v, V, or ^V). |
:%Dec2hex |
Same, for all lines in buffer. |
:Hex2dec 0x1f0 |
Displays 496 (decimal equivalent of hex 1f0). |
:Hex2dec 1f0 |
Same ("0x" is optional in an argument). |
:Hex2dec |
Converts all "0x" hex numbers to decimal in current line. |
:'<,'>Hex2dec |
Same, for all visually selected text (v, V, or ^V). |
:%Hex2dec |
Same, for all lines in buffer. |
This version handles up to 32-bit long integers. An extended version of this script that works for arbitrary sized integers is available as a plugin on Github.
Converting strings[]
Following are some methods for working with percent-encoded text, and for showing ASCII characters in hex.
" Convert current line to percent-encoded hex for disallowed punctuation. " Example: line "A/C[123]D\E" is converted to "A%2FC%5B123%5DD%5CE". nnoremap <Leader>h :s@\([;(){}\[\]+ ,\-><\|=%&^\\/"']\)@\='%'.printf('%02X',char2nr(submatch(1)))@g<CR> " Convert percent-encoded hex in current line to text (reverse of above). nnoremap <Leader>H :s@%\(\x\x\)@\=nr2char('0x'.submatch(1))@g<CR> " Convert each ASCII character in a string to hex bytes. " Example: ":Str2hex ABC 123" displays "41 42 43 20 31 32 33". command! -nargs=* Str2hex echo Str2hex(<q-args>) function! Str2hex(arg) return join(map(split(a:arg, '\zs'), 'printf("%02x", char2nr(v:val))')) endfunction
General functions[]
A script could use the following functions for conversions between decimal and hex.
" Return hex string equivalent to given decimal string or number. function! Dec2hex(arg) return printf('%x', a:arg + 0) endfunction " Return number equivalent to given hex string ('0x' is optional). function! Hex2dec(arg) return (a:arg =~? '^0x') ? a:arg + 0 : ('0x'.a:arg) + 0 endfunction
Sometimes one just needs to know the value of decimal/hexadecimal value, without changing the text. Put the following in your vimrc to define user command 'gn' to print the number under the cursor converted to hex/decimal (similar to built-in command 'ga' and 'g8' for ASCII character under the cursor):
nnoremap gn :call DecAndHex(expand("<cWORD>"))<CR> function! DecAndHex(number) let ns = '[.,;:''"<>()^_lL]' " number separators if a:number =~? '^' . ns. '*[-+]\?\d\+' . ns . '*$' let dec = substitute(a:number, '[^0-9+-]*\([+-]\?\d\+\).*','\1','') echo dec . printf(' -> 0x%X, -(0x%X)', dec, -dec) elseif a:number =~? '^' . ns. '*\%\(h''\|0x\|#\)\?\(\x\+\)' . ns . '*$' let hex = substitute(a:number, '.\{-}\%\(h''\|0x\|#\)\?\(\x\+\).*','\1','') echon '0x' . hex . printf(' -> %d', eval('0x'.hex)) if strpart(hex, 0,1) =~? '[89a-f]' && strlen(hex) =~? '2\|4\|6' " for 8/16/24 bits numbers print the equivalent negative number echon ' ('. float2nr(eval('0x'. hex) - pow(2,4*strlen(hex))) . ')' endif echo else echo "NaN" endif endfunction
Numbers containing character A-F or prefixed with '0x', 'h' or '#' are treated as hexadecimal values:
WORD under cursor | Output | Description |
---|---|---|
32 |
32 -> 0x20, -(0xFFFFFFE0) | decimal 32 in hex, decimal -32 in hex |
-32 |
-32 -> 0xFFFFFFE0, -(0x20) | decimal -32 in hex, decimal 32 in hex |
0x32 |
0x32 -> 50 | hex 32 in decimal |
h'38 |
0x38 -> 56 | hex 38 in decimal |
#123 |
0x123 -> 291 | hex 123 in decimal |
0xFFFFFFE0 |
0xFFFFFFE0 -> -32 | 32 bit hex FFFFFFE0 in decimal |
0xFFFE00 |
0xFFFE00 -> 16776704 (-512) | hex FFFE00 in decimal, equivalent negative value on a 24 bits machine |
ab |
0xab -> 171 (-85) | hex ab in decimal, equivalent negative value on a 8 bits machine |
Using external programs[]
TO DO
- Fix or delete this section.
- The following is from old tip 772. It does not seem helpful, but we should discuss the menus somewhere so I am keeping the text for a while.
This example creates a menu for conversions using the bc calculator which is a standard utility on many Unix-based systems. Visually select the number (without leading '0x'), right click the selection, and select from the popup menu to transform the number.
vmenu 1.220 PopUp.&nr2hex <Esc>:exec("!echo \\"obase=16;".@*."\\" \| bc -l -q ")<CR> vmenu 1.220 PopUp.hex&2nr <Esc>:exec("!echo \\"ibase=16;".toupper(@*)."\\" \| bc -l -q ")<CR>
More is needed to make it work. I had to do the following on a Linux system, but I suspect a setting regarding register *
is also being used (it assumes that the selected text is in the *
register).
set mousemodel=popup vmenu 1.220 PopUp.&nr2hex <Esc>:exec '!echo "obase=16;'.@*.'" \| bc -l -q '<CR> vmenu 1.220 PopUp.hex&2nr <Esc>:exec '!echo "ibase=16;'.toupper(@*).'" \| bc -l -q '<CR>
For one of my recent Machine learning project UI, I had to create a hex to decimal converter in Javascript. You can use the following Javascript code: See hex to decimal working with Javascript
function hextodec() { var mm = document.getElementById("text_value").value; var x = new BigNumber(mm, 16); var dect = x.toString(10); document.getElementById("ans").innerHTML = dect; }
See also[]
- Hex dump editing or displaying binary files in hex
- Improved hex editing automating some of the procedures to edit binary files in hex
- How to convert from decimal to hexManual hex to decimal conversion
- ConvertBase plugin to convert to/from various numeric bases
- Convert Hexadecimal to Decimal Number online tool to convert hex to dec
- From one to another number system, article related to creating computer program for conversion of number from one to another number system with source code written in C#