如果你能找到一个免费的Pascal编译器，你就可以编译它。至少它可以工作，并且显示了必要的算法。

program Whence (input, output);
  Uses Dos, my_funk;
  Const program_version = '1.00';
        program_date    = '17 March 1994';
  VAR   path_str          : string;
        command_name      : NameStr;
        command_extension : ExtStr;
        command_directory : DirStr;
        search_dir        : DirStr;
        result            : DirStr;


  procedure Check_for (file_name : string);
    { Check existence of the passed parameter. If exists, then state so   }
    { and exit.                                                           }
  begin
    if Fsearch(file_name, '') <> '' then
    begin
      WriteLn('DOS command = ', Fexpand(file_name));
      Halt(0);    { structured ? whaddayamean structured ? }
    end;
  end;

  function Get_next_dir : DirStr;
    { Returns the next directory from the path variable, truncating the   }
    { variable every time. Implicit input (but not passed as parameter)   }
    { is, therefore, path_str                                             }
    var  semic_pos : Byte;

  begin
      semic_pos := Pos(';', path_str);
      if (semic_pos = 0) then
      begin
        Get_next_dir := '';
        Exit;
      end;

      result := Copy(Path_str, 1, (semic_pos - 1));  { return result   }
      { Hmm! although *I* never reference a Root drive (my directory tree) }
      { is 1/2 way structured), some network logon software which I run    }
      { does (it adds Z:\ to the path). This means that I have to allow    }
      { path entries with & without a terminating backslash. I'll delete   }
      { anysuch here since I always add one in the main program below.     }
      if (Copy(result, (Length(result)), 1) = '\') then
         Delete(result, Length(result), 1);

      path_str := Copy(path_str,(semic_pos + 1),
                       (length(path_str) - semic_pos));
      Get_next_dir := result;
  end;  { Of function get_next_dir }

begin
  { The following is a kludge which makes the function Get_next_dir easier  }
  { to implement. By appending a semi-colon to the end of the path         }
  { Get_next_dir doesn't need to handle the special case of the last entry }
  { which normally doesn't have a semic afterwards. It may be a kludge,    }
  { but it's a documented kludge (you might even call it a refinement).    }
  path_str := GetEnv('Path') + ';';

  if (paramCount = 0) then
  begin
    WriteLn('Whence: V', program_version, ' from ', program_date);
    Writeln;
    WriteLn('Usage: WHENCE command[.extension]');
    WriteLn;
    WriteLn('Whence is a ''find file''type utility witha difference');
    Writeln('There are are already more than enough of those :-)');
    Write  ('Use Whence when you''re not sure where a command which you ');
    WriteLn('want to invoke');
    WriteLn('actually resides.');
    Write  ('If you intend to invoke the command with an extension e.g ');
    Writeln('"my_cmd.exe param"');
    Write  ('then invoke Whence with the same extension e.g ');
    WriteLn('"Whence my_cmd.exe"');
    Write  ('otherwise a simple "Whence my_cmd" will suffice; Whence will ');
    Write  ('then search the current directory and each directory in the ');
    Write  ('for My_cmd.com, then My_cmd.exe and lastly for my_cmd.bat, ');
    Write  ('just as DOS does');
    Halt(0);
  end;

  Fsplit(paramStr(1), command_directory, command_name, command_extension);
  if (command_directory <> '') then
  begin
WriteLn('directory detected *', command_directory, '*');
    Halt(0);
  end;

  if (command_extension <> '') then
  begin
    path_str := Fsearch(paramstr(1), '');    { Current directory }
    if   (path_str <> '') then WriteLn('Dos command = "', Fexpand(path_str), '"')
    else
    begin
      path_str := Fsearch(paramstr(1), GetEnv('path'));
      if (path_str <> '') then WriteLn('Dos command = "', Fexpand(path_str), '"')
                          else Writeln('command not found in path.');
    end;
  end
  else
  begin
    { O.K, the way it works, DOS looks for a command firstly in the current  }
    { directory, then in each directory in the Path. If no extension is      }
    { given and several commands of the same name exist, then .COM has       }
    { priority over .EXE, has priority over .BAT                             }

    Check_for(paramstr(1) + '.com');     { won't return if file is found }
    Check_for(paramstr(1) + '.exe');
    Check_for(paramstr(1) + '.bat');

    { Not in current directory, search through path ... }

    search_dir := Get_next_dir;

    while (search_dir <> '') do
    begin
       Check_for(search_dir + '\' + paramstr(1) + '.com');
       Check_for(search_dir + '\' + paramstr(1) + '.exe');
       Check_for(search_dir + '\' + paramstr(1) + '.bat');
       search_dir := Get_next_dir;
    end;

    WriteLn('DOS command not found: ', paramstr(1));
  end;
end.

在PowerShell下，Get命令将在$Env:PATH中的任何位置找到可执行文件。

$ Get-Command eventvwr

CommandType   Name          Definition
-----------   ----          ----------
Application   eventvwr.exe  c:\windows\system32\eventvwr.exe
Application   eventvwr.msc  c:\windows\system32\eventvwr.msc

因为powershell让我们定义别名，可以这样定义。

$ sal which gcm   # short form of `Set-Alias which Get-Command`
$ which foo
...

PowerShell命令不仅仅是可执行文件（.exe、.ps1等）。它们也可以是cmdlet、函数、别名、在$Env:PATHEXT中设置的自定义可执行后缀等。Get Command能够查找并列出所有这些命令（与Bash的类型-a foo非常相似）。仅这一点就比where.exe、which.exe等（通常仅限于查找可执行文件）更好。

仅使用部分名称查找可执行文件

$ gcm *disk*

CommandType     Name                             Version    Source
-----------     ----                             -------    ------
Alias           Disable-PhysicalDiskIndication   2.0.0.0    Storage
Alias           Enable-PhysicalDiskIndication    2.0.0.0    Storage
Function        Add-PhysicalDisk                 2.0.0.0    Storage
Function        Add-VirtualDiskToMaskingSet      2.0.0.0    Storage
Function        Clear-Disk                       2.0.0.0    Storage
Cmdlet          Get-PmemDisk                     1.0.0.0    PersistentMemory
Cmdlet          New-PmemDisk                     1.0.0.0    PersistentMemory
Cmdlet          Remove-PmemDisk                  1.0.0.0    PersistentMemory
Application     diskmgmt.msc                     0.0.0.0    C:\WINDOWS\system32\diskmgmt.msc
Application     diskpart.exe                     10.0.17... C:\WINDOWS\system32\diskpart.exe
Application     diskperf.exe                     10.0.17... C:\WINDOWS\system32\diskperf.exe
Application     diskraid.exe                     10.0.17... C:\WINDOWS\system32\diskraid.exe
...

查找自定义可执行文件

与UNIX不同，在UNIX中，可执行文件是设置了可执行（+x）位的文件，而windows上的可执行文件则是$PATH env中指定的一个目录中的文件。其文件名后缀在$PATHEXT env中命名的变量。变量（默认为.COM；.EXE；.BAT；.CMD；.VBS；.VBE；.JS；.JSE；.WSF；.WSH；.MSC；.CPL）。

作为Get Command，也将此env作为荣誉。变量，它可以扩展为列出自定义可执行文件。例如

$ $Env:PATHEXT="$Env:PATHEXT;.dll;.ps1;.psm1;.py"     # temporary assignment, only for this shell's process

$ gcm user32,kernel32,*WASM*,*http*py

CommandType     Name                        Version    Source
-----------     ----                        -------    ------
ExternalScript  Invoke-WASMProfiler.ps1                C:\WINDOWS\System32\WindowsPowerShell\v1.0\Invoke-WASMProfiler.ps1
Application     http-server.py              0.0.0.0    C:\Users\ME\AppData\Local\Microsoft\WindowsApps\http-server.py
Application     kernel32.dll                10.0.17... C:\WINDOWS\system32\kernel32.dll
Application     user32.dll                  10.0.17... C:\WINDOWS\system32\user32.dll

有关更多选项和示例，请参见获取命令。

只需发布此Windows的单行批处理文件：

C:>type wh.cmd
@for %%f in (%*) do for %%e in (%PATHEXT% .dll .lnk) do for %%b in (%%f%%e) do for %%d in (%PATH%) do if exist %%d\%%b echo %%d\%%b

A测试：

C:>wh ssh
C:\cygwin64\bin\ssh.EXE
C:\Windows\System32\OpenSSH\\ssh.EXE

如果将代码包装在setlocalenableextensions和endlocal中，那就不是一行了。

我已经使用npm中的which模块很长时间了，它工作得很好：https://www.npmjs.com/package/which这是一个很好的多平台替代方案。

现在我切换到Git附带的。只需将Git中的/usr/bin路径添加到路径中，该路径通常位于C:\Program Files\Git\usr\bin\which.exe。哪个二进制文件位于C:\Program Files \Git\usr/bin\which.exe。它速度更快，也能按预期工作。

虽然较新版本的Windows具有where命令，但您也可以使用环境变量修饰符在Windows XP中执行此操作，如下所示：

c:\> for %i in (cmd.exe) do @echo.   %~$PATH:i
   C:\WINDOWS\system32\cmd.exe

c:\> for %i in (python.exe) do @echo.   %~$PATH:i
   C:\Python25\python.exe

您不需要任何额外的工具，也不限于PATH，因为您可以替换任何您希望使用的环境变量（当然是路径格式）。

而且，如果你想要一个能够处理PATHEXT中所有扩展的系统（就像Windows本身一样），这个系统可以做到：

@echo off
setlocal enableextensions enabledelayedexpansion

:: Needs an argument.

if "x%1"=="x" (
    echo Usage: which ^<progName^>
    goto :end
)

:: First try the unadorned filenmame.

set fullspec=
call :find_it %1

:: Then try all adorned filenames in order.

set mypathext=!pathext!
:loop1
    :: Stop if found or out of extensions.

    if "x!mypathext!"=="x" goto :loop1end

    :: Get the next extension and try it.

    for /f "delims=;" %%j in ("!mypathext!") do set myext=%%j
    call :find_it %1!myext!

:: Remove the extension (not overly efficient but it works).

:loop2
    if not "x!myext!"=="x" (
        set myext=!myext:~1!
        set mypathext=!mypathext:~1!
        goto :loop2
    )
    if not "x!mypathext!"=="x" set mypathext=!mypathext:~1!

    goto :loop1
:loop1end

:end
endlocal
goto :eof

:: Function to find and print a file in the path.

:find_it
    for %%i in (%1) do set fullspec=%%~$PATH:i
    if not "x!fullspec!"=="x" @echo.   !fullspec!
    goto :eof

它实际上返回所有可能性，但您可以很容易地针对特定搜索规则进行调整。

从这里获取unxutils：http://sourceforge.net/projects/unxutils/

在windows平台上的黄金，将所有漂亮的unix实用程序放在标准的windows DOS上。多年来一直在使用它。

它包含一个“which”。注意，它是区分大小写的。

注意：要安装它，请在某个地方爆炸拉链并添加。。。\将xUtils\usr\local\wbin\解压缩到系统路径env变量。