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   The second is that DOS paths may include an optional drive name such   
   as C: and... the drive name has the colon character int. While Unix   
   uses the colon character to separate multiple components of the   
   search PATH, DOS could not do that: it had to pick a different   
   character, and it picked the semicolon. Take a look:   
      
       C:\>path   
       PATH=Z:\;C:\DEVEL\BIN;C:\DEVEL\DJGPP\BIN;C:\DEVEL\TC\BIN   
      
   The problem here is that many Unix applications, particularly shell   
   scripts like configure--especially configure--read the value of the   
   PATH variable and split it at colon separators or append to it by   
   adding a colon. But if we do these textual manipulations on a   
   DOS-style PATH like the one shown above... we'll get the wrong   
   behavior because of the drive names--and Unix programs don't know   
   they have to split on the semicolon instead and we cannot be expected   
   to fix them all.   
      
   The way DJGPP deals with this is by faking the /dev/ device tree.   
   While DJGPP provides implementations of things like /dev/null, it   
   also exposes DOS drives via their corresponding /dev/[a-z]/ virtual   
   directory. So, if you wanted to run applications that parse or modify   
   the PATH, you could rewrite the above as this:   
      
       PATH=/dev/z:/dev/c/devel/bin:/dev/c/devel/djgpp/bin:/dev/c/devel/tc/bin   
      
   This would allow any application reading the PATH to continue to   
   work. But note that this value doesn't seem to leave the realm of the   
   current process, which is interesting:   
      
       D:\>path   
       PATH=Z:\;C:\DEVEL\BIN;C:\DJGPP\BIN;C:\DEVEL\TC\BIN   
       D:\>   
          
       D:\>bash   
       bash-4.2$ echo $PATH   
       z:/;c:/devel/bin;c:/djgpp/bin;c:/devel/tc/bin   
       bash-4.2$ env | grep ^PATH=   
       PATH=z:/;c:/devel/bin;c:/djgpp/bin;c:/devel/tc/bin   
       bash-4.2$   
       bash-4.2$ PATH=/dev/c/djgpp/bin   
       bash-4.2$   
       bash-4.2$ echo $PATH   
       /dev/c/djgpp/bin   
       bash-4.2$ env | grep ^PATH=   
       PATH=c:\djgpp\bin   
       bash-4.2$   
      
   The picture above shows how bash sees a DOS-style PATH after it   
   starts. Manually setting it to a Unix path keeps the Unix path in the   
   current process (as shown by the built-in echo calls), but when we   
   spawn a different one (env is a separate executable), the value is   
   reset. This makes sense because, if we are running a regular DOS   
   program from within a DJGPP one, we want to export a DOS-compatible   
   environment. Which means the Unix variants probably only stick within   
   shell scripts. You can also see how this works by peeking at   
   dosexec.c again.   
      
   But wait a minute... did I just show you bash?! On DOS? Oh yes, yes I   
   did...   
      
   # Trying it out yourself   
      
   It's time to get our hands dirty, try this out, and reminisce the old   
   days! Or, actually, not so old. You should know that DJGPP is still   
   available in this day and age and that it is quite up to date with   
   GCC 12.3--released less than a year ago.   
      
   First off, start by installing DOSBox. You can use the standard   
   DOSBox version, but it's probably better to go the DOSBox-X route so   
   that you can get Long File Name (LFN) support by setting the ver=7.1   
   configuration option. Otherwise, beware that running Bash later on   
   will create .bash_history under C:\ but the file will be named .BAS   
   due to some odd truncation, and this will later confuse Bash on a   
   second start and assume that .BAS is actually .bash_login.   
      
      
      
      
      
   Now, pick a mirror for your downloads. You'll see various uses of FTP   
   in the list but don't be surprised if clicking on those doesn't work:   
   major browsers have unfortunately dropped their FTP client so you'll   
   have to "fall back" to an HTTP mirror.   
      
      
      
   From there, you can use the Zip Picker to help you choose what you   
   need or you can download the same files I did:   
      
   * v2apps/csdpmi7b.zip:  The CWSDPMI free DPMI host.   
   * v2apps/rhid15ab.zip:  The RHIDE console IDE akin to Turbo C++.   
   * v2/djdev205.zip:      Base DJGPP tools.   
   * v2gnu/bnu2351b.zip:   GNU Binutils (tools like gas and objdump).   
   * v2gnu/bsh4253b.zip:   GNU Bash.   
   * v2gnu/em2802b.zip:    GNU Emacs.   
   * v2gnu/fil41br3.zip:   GNU coreutils (tools like ls and cp).   
   * v2gnu/gcc930b.zip:    GCC itself.   
   * v2gnu/gdb801b.zip:    GDB because why not.   
   * v2gnu/gpp930b.zip:    G++.   
   * v2gnu/grep228b.zip:   grep because I find it very handy.   
   * v2gnu/mak44b.zip:     GNU Make.   
   * v2gnu/shl2011br3.zip: Various shell utilities (*)   
   * v2gnu/txt20br3.zip:   GNU textutils (tools like cat and cut).   
      
   (*) (like basename and dirname) that you'll almost-certainly need to   
       run shell scripts.   
      
   Once you have those files, create the "root" directory for what will   
   be the C: drive in DOSBox. I keep this under ~/dos/ and it is much   
   easier to prepare this directory from outside of DOSBox. Within that   
   location, create a djgpp subdirectory and unpack all the zip files   
   you downloaded into it. If there are any file conflicts, just tell   
   unzip to overwrite them.   
      
   Once the unpacking finishes, go to your DOSBox configuration. If you   
   are on Windows, you should have a start menu entry called "DOSBox   
   0.74-3 Options" or similar which opens the configuration file in   
   Notepad. If you are on Linux or any other reasonable OS, you can find   
   the configuration file under ~/.dosbox/. In the configuration, you'll   
   want to set up the C: drive at the very bottom of the file where the   
   [autoexec] section is. Here is what I do:   
      
       [autoexec]   
       MOUNT C C:\Users\jmmv\dos   
       SET PATH=%PATH%;C:\DJGPP\BIN   
       SET DJGPP=C:\DJGPP\DJGPP.ENV   
       C:   
      
   Launch DOSBox and you are set. Enter full-screen by pressing   
   Alt+Enter for the full retro experience and then... launch   
   bash:   
      
       C:\>gcc   
       gcc.exe: fatal error: no input files   
       compilation terminated.   
          
       C:\>bash   
       bash-4.2$ uname -a   
       MS-DOS #= Don't 5 00 i486 unknown   
       bash-4.2$ gcc   
       gcc.exe: fatal error: no input files   
       compilation terminated.   
       bash-4.2$ pwd   
       c:/   
       bash-4.2$ ls djgpp   
       allegro  copying     djgpp.env  include  libexec     share   
       bin      copying.dj  faq        info     manifest    tmp   
       contrib  copying.lib gnu        lib      readme.1st   
       bash-4.2$ date   
       Sat Feb 10 11:09:51 GMT 2024   
       bash-4.2$ _   
      
   Pretty neat stuff, huh?   
      
   From:    
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