Text editor capable of viewing invisibles?

Question

A recent problem* left me wondering whether there is a text editor out there that lets you see every single character of the file, even if they are invisible? Specifically, I'm not looking for hex editing capabilities, I am interested in a text editor that'll show me all of the invisible characters (not just the common whitespace / line break characters). The BOM marker is just one example, others are e.g. mathematical invisibles or possibly unsupported characters.

I'm not looking for a text editor that simply supports a large variety of text encoding / translations between encodings. All text editors I've come across treat the invisible characters correctly i.e. leave them invisible (or simply get removed in the translation as in the case of the BOM marker).

I'm asking this mostly out of academic interests, so I'm not particular about any specific OS. I can easily test Linux and OSX solutions, but if you recommend a Windows editor, I would appreciate if you include descriptions of how the editor handles invisibles other than whitespace / line breaks.

EDIT: I'm beginning to be sure that the behavior I want can be implemented in emacs/vim via either custom highlighting or by messing around with the font itself. A solution of this type would also be acceptable.

EDIT2: After looking at several options I found TextMate which at least shows a blank space where an invisible UTF-8 character is in the file. Slightly disappointed with SO's ability to answer my question. Bounty goes to VIM, because that is the direction in which the solution most likely lies.

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*The incident that lead me to this question: I wrote a perl script using TextWrangler and managed to change the encoding to UTF8 BOM, which inserts the BOM marker at the start of the file. Perl (or rather the operating system) promptly misses the #! and mayhem ensues. It then took me the better part of an afternoon to figure this out since most text editors do not show the BOM marker even with various "show invisibles" options turned on. Now I've learned my lesson and will use less immediately :-).

Answer 1

Notepad++ rocks:

Answer 2

Open the file in EMACS and do a M-X hexl-mode. You'll get a display that looks like this:

87654321  0011 2233 4455 6677 8899 aabb ccdd eeff  0123456789abcdef                               
00000000: 2320 2020 2020 2020 2020 2020 2020 2020  #               
00000010: 2020 2020 2020 2020 2020 2020 2020 2020                  
00000020: 2020 2020 2020 2020 2020 2020 2020 2020                  
00000030: 2d2a 2d20 4175 746f 636f 6e66 202d 2a2d  -*- Autoconf -*-
00000040: 0a23 2050 726f 6365 7373 2074 6869 7320  .# Process this 
00000050: 6669 6c65 2077 6974 6820 6175 746f 636f  file with autoco
00000060: 6e66 2074 6f20 7072 6f64 7563 6520 6120  nf to produce a 
00000070: 636f 6e66 6967 7572 6520 7363 7269 7074  configure script
00000080: 2e0a 2320 4f72 6465 7220 6973 206c 6172  ..# Order is lar
00000090: 6765 6c79 2069 7272 6576 656c 6c61 6e74  gely irrevellant
000000a0: 2c20 616c 7468 6f75 6768 2069 7420 6d75  , although it mu
000000b0: 7374 2073 7461 7274 2077 6974 6820 4143  st start with AC
000000c0: 5f49 4e49 5420 616e 6420 656e 6420 7769  _INIT and end wi
000000d0: 7468 2041 435f 4f55 5450 5554 0a23 2053  th AC_OUTPUT.# S
000000e0: 6565 2068 7474 703a 2f2f 6175 746f 746f  ee http://autoto
000000f0: 6f6c 7365 742e 736f 7572 6365 666f 7267  olset.sourceforg
00000100: 652e 6e65 742f 7475 746f 7269 616c 2e68  e.net/tutorial.h

Answer 3

In Visual Studio's Open File dialog, the Open pushbutton has a down arrow next to it that lets you choose Open With.... One of the options in the resulting dialog is Binary Editor.

I've used this now and then to spot some invisible character or to resolve some line-ending issue.

Answer 4

If you are running a 32 bit version of windows, you can see BOMs and other invisible characters such as carriage return or line feeds that look like a music eighth note in MS Dos Editor which you can open by typing "edit" in the run box or from a command prompt. Unfortunately, the ms dos editor is not available on 64 bit systems :(

Answer 5

vim (in either textual or graphic mode) can show all control characters if you :set list. The BOM is a special case, controlled by the :set bomb or :set nobomb commands.

Answer 6

You can also user Notepad ++ to show them. Here is an example, the black boxes are control characters.