Tcl on Windows FAQ (2020-07-01)

Table of Contents

1 About this FAQ

This FAQ is targeted towards using Tcl on Windows. Specifically, it addresses the most recent release of Tcl (8.6) on Windows XP or later. Some examples will not work with older versions of Tcl.

The FAQ does not address general Tcl platform-independent features. Nor does it address questions related to the graphical toolkit Tk.

2 About Tcl

2.1 What is Tcl and why should I learn it?

Tcl is a high-level dynamic language that runs on a wide variety of platforms, from mainstream operating systems like Unix/Linux, Windows and MacOS to embedded systesm like Cisco routers. Code written on one platform will run practically unchanged on another. Tcl's simple but powerful and expressive nature make it suitable for applications ranging from customized systems administration utilities to standalone desktop applications to scalable, distributed servers.

2.2 What is Tk ?

Tk is a toolkit for building cross-platform graphical user interfaces. Although bindings exist for other languages such as Perl and Python, it was originally built as a complement to Tcl and has the tightest binding to that language. Hence, the two are most commonly refered together as Tcl/Tk. This FAQ focuses only on Tcl and does NOT address Tk-related questions.

2.3 What Windows platforms does Tcl support ?

The current release of Tcl, Version 8.6, requires Windows XP or later. The previous release, version 8.5, also supports Windows Windows 2000. Earlier versions of Windows, Windows NT 4.0 and the Windows 98 series, require Tcl 8.4 and are not covered by this FAQ.

2.4 How is Tcl licensed? Can I use it in commercial applications?

Tcl is covered under the very liberal open source BSD license. This means Tcl and its associated libraries can be used in all applications, including commercial ones.

Specific binary distributions may have their own licenses.

2.5 Where can I find documentation for Tcl?

The official reference documentation for Tcl 8.6 is available at A searchable index for Tcl/Tk along with several popular extensions is available at

The Tcl web site lists several books on Tcl/Tk. In addition, there is an online book specific to programming with Tcl on Windows.

2.6 Is there a Tcl tutorial?

See the online Tcl tutorial. In addition, the Tcler's Wiki provides tutorials, explanations and sample code in all areas. It is also an excellent jump point to the various Tcl resources on the net.

2.7 Where can I get help on Tcl?

You can get questions answered on the comp.lang.tcl newsgroup or the #tcl channel on

2.8 How do I keep up with news from the Tcl world?

There is Twitter feed for for Tcl-related news, including new releases of Tcl and extensions. The comp.lang.tcl newsgroup and the Tcler's Wiki are other places to visit for announcements and such.

3 Installing Tcl

3.1 What Tcl distributions are available for Windows?

There are several freely downloadable binary distributions of Tcl available. See the Binary Distributions page.

3.2 Are there any single-executable distributions of Tcl?

There are several distributions of Tcl that consist of a single executable file. These distributions also support binding your applications scripts within the executable so that your entire application itself can be distributed as a single executable. The most commonly used ones are tclkit and freewrap. You can also create your own versions from the KitCreator site.

Pre-built executables are available from or the TWAPI download area.

4 General Usage

4.1 What are tclsh and wish?

Windows distinguishes between console mode and graphical interface programs. Tcl distributions correspondingly come with two different programs, tclsh.exe and wish.exe. The former is used for scripts that run in console mode and the latter for applications with a graphical user interface, generally based on Tk.

Depending on the actual Tcl distribution being used, the executables may be named differently, for example tclsh86t.exe and wish86t.exe.

4.2 How do I run Tcl in interactive mode?

To run the Tcl interpreter, so that you can interactively invoke Tcl commands, simply type in the name of the appropriate executable. This will display a Tcl shell prompt where you can type in commands.

1: c:\> tclsh
2: % puts "Hello world"
3: Hello world
4: % exit
5: c:>

4.3 How do I run a Tcl script from the command line?

To run a console script, invoke the tclsh.exe program, passing it the path to the script file. Any additional arguments on the command line are passed as a list to the script in the argv global variable.

1: # File printargs.tcl
2: foreach arg $::argv {puts $arg} 

We can invoke this script from the command line:

1: c:\> tclsh printargs.tcl first "second arg"
2: first
3: second arg
4: c:\>

4.4 How can I associate a Tcl script with the Tcl interpreter application?

Windows can associate a file with an application so that typing the name of the file will result in the application being invoked. Many binary distributions will give you the option of associating specific extensions with Tcl or Tk. Alternatively, you can set or change the association from the File Types tab in the Folder Options dialog in Explorer.

In addition, if you want to run the script from the command line simply by typing its name, add the extension to the PATHEXT environment variable.

You may wish to associate separate extensions, for example .tcl and .tk, depending on whether you want the script invoked with tclsh or wish.

4.5 How can I invoke a Tcl script from Explorer?

In order to run a Tcl script by double-clicking the script file, the file type must be associated with the Tcl shell. See the previous entry in this FAQ.

4.6 How can I embed a Tcl script in a batch file?

As an alternative to making .tcl files directly executable, you may prefer to make scripts executable by embedding them in batch files. For example, assume printargs.bat is somewhere in your PATH and contains the following:

1: ::if no {
2: @tclsh "%~f0" %*
3: @goto :eof 
4: }
5: # Tcl code start
7: foreach arg $argv { puts $arg }
8: # Tcl code end \
9: :eof

Invoking the file:

1: C:\>printargs first "second arg"
2: first
3: second arg

See an explanation of the above and more sophisticated versions in the Tcl wiki.

4.7 How can I have Tcl always execute a certain set of commands on starting?

On startup, tclsh.exe reads and executes commands in the file tclshrc.tcl in the user's home directory. The user's home directory is given by the environment variable USERPROFILE or can be displayed with the Tcl command

% file normalize ~

4.8 When should I use a Tcl extension versus an external program?

Some tasks can be accomplished from Tcl by invoking external programs or through the use of a Tcl extension (example). If you are writing a one-off script with limited use or the command is rarely invoked, using an external program might be sufficient. In other cases, use of an extension is likely to be beneficial. It is generally much faster and also protects against the external program not being available or installed on the target system (this is true even for Windows components) and differences arising from localization.

5 General Windows programming

5.1 How can I access the Windows registry?

Tcl provides the registry command for doing various operations on the Windows registry. You will need to load the registry package first:

1: % package require registry
2: % registry get HKEY_CURRENT_USER\\Environment PATH
3: c:\bin;c:\tcl\tcl86\bin;c:\msys\bin

5.2 How can I get system information?

The Tcl global array tcl_platform provides basic information about the system such as the operating system, version number etc. Additional information is provided in the Windows environment variables which can be accessed via the global env array. For more extensive details, use the osinfo module in the TWAPI extension.

5.3 How can I print from a script?

The TkPrint or Printer extensions may be used for printing under Windows.

6 Processes

6.1 How can I start a new process?

Tcl provides the exec command for starting new processes. The command supports pipes with multiple subprocesses, I/O redirection and background processes. The following commands all start a copy of notepad:

1: % exec notepad.exe &
2: % exec c:/windows/system32/notepad.exe &
3: % exec {*}[auto_execok notepad] &

Line 1 assumes notepad.exe is in a directory in your PATH environment variable. Line 2 explicitly specifies the path to the program. Line 3 makes use of the auto_execok command which returns the full command line required for invocation filling in the path, extension if missing as well as checking for cmd.exe built-in commands.

1: % auto_execok notepad
2: C:/WINDOWS/system32/notepad.EXE
3: % auto_execok dir
4: C:/WINDOWS/system32/cmd.exe /c dir

Line 1 returns the path to notepad.exe. Line 3 returns the command line to invoke an internal cmd.exe command.

For additional control over the child process, such as its display properties, security attributes, priority etc., use the create_process command from the TWAPI extension.

6.2 How can I read from and write to a child process?

Use the Tcl open command to open a pipe by prefixing the child process command line with a | character. Then read and write using the standard Tcl I/O commands puts. gets, read etc.

1: % set fd [open "| cmd.exe /c dir"]
2: file94e0d8
3: % while {![eof $fd]} {puts [gets $fd]}
4: % close $fd

6.3 How can I launch a document or URL?

To start up an application associated with a file or URL, invoke the Windows cmd.exe internal start command. For example,

% exec {*}[auto_execok start] "" myfile.doc &
% exec {*}[auto_execok start] "" &

Alternatively, see the next entry.

6.4 How can I invoke an action, like print, on a document?

The Windows Explorer Shell associates certain actions that can be carried out on a document based on its file type. These actions, such as Open, Edit, Print can be invoked from the right-click menu in Explorer. To invoke the action using Tcl, use the shell_execute command from the TWAPI extension.

The following will use the default action Open to start editing the file with Microsoft Word.

twapi::shell_execute -path sample.doc

To print the file:

twapi::shell_execute -path sample.doc -verb print

To compose an email message:

twapi::shell_execute -path mailto:[email protected]

6.5 How can I start a privileged process under UAC?

Windows Vista and later versions implement User Account Control (UAC) under which even processes belonging to privileged accounts run with reduced privileges unless explicitly elevated by the user. To start a process in elevated mode, use the shell_execute command from the TWAPI extension with the runas action.

twapi::shell_execute -verb runas -path services.msc

6.6 How can I terminate a process?

The TWAPI extension provides the end_process command for this purpose.

twapi::end_process 1234
foreach pid [twapi::get_process_ids -name notepad.exe] {twapi::end_process $pid}

As an alternative, you can invoke the Windows command line program taskkill.exe using Tcl's exec command to terminate a process by its PID or name.

1: exec {*}[auto_execok taskkill] /PID 1234
2: exec {*}[auto_execok taskkill] /IM notepad.exe

6.7 How can I write a Windows service using Tcl?

There are several options for running a Tcl script as a Windows service:

  • The TWAPI extension's run_as_service command. The online book chapter Windows Services provides a detailed guide to writing and managing services using TWAPI.
  • ActiveState's Tcl Development Kit provides a tool to wrap a Tcl script as a Windows service
  • Generic programs such as Firedaemon and winserv can also be used to run a Tcl script as a Windows service by spawning tclsh.exe as a child process.

7 Files and Disks

7.1 What file path separator should I in Tcl?

Like the Windows kernel (as opposed to the Windows DOS command prompt), Tcl will accept either / or \ as a directory separator in a file path. However, like in other languages such as C, \ is also used in Tcl syntax to indicate an escape sequence. Hence when used in a literal it needs to be doubled:

% file exists c:\\windows\\system32

In some cases, such as executing an external program that expects \ as the directory separator, you can use the file nativename command to convert a path:

% file nativename c:/windows/system32

7.2 How can I get a list of drives in the system?

Use Tcl's file volumes command.

% file volumes
C:/ D:/

7.3 How can I access files on remote shares?

Tcl understands UNC names of the form \\SERVER\SHARE\some\file so the standard Tcl I/O commands can be used to open and access files on remote shares.

7.4 How can I monitor changes to the file system?

You can either use the Tcl glob command to read a directory and poll for changes or use the TWAPI extension as shown in the session below. Both methods have their advantages and disadvantages. Polling can be expensive as the entire directory tree has to be read and compared. The TWAPI method uses Windows notification as and when changes occur and has filtering options. On the other hand, notifications are not guaranteed to be delivered under load. Reliability is particularly an issue with remote file systems. You may wish to use a combination of the two methods depending on the application.

The sample below illustrates use of TWAPI's begin_filesystem_monitor command:

1: % proc pargs args {puts [join $args ,]}
2: % set notifier [twapi::begin_filesystem_monitor C:/windows pargs -subtree true -write true -patterns {*.exe *.dll}]
3: % puts stderr "Type Ctrl-C to exit"
4: % vwait forever

This command will print a line whenever an executable (.exe or .dll) is written to anywhere under the Windows directory. The vwait command is required in this small example as notifications require the Tcl event loop to be running.

7.5 How can I get device notifications such as CD or pen drive insertion?

Use the TWAPI extension as shown in the session below. (IMPORTANT: The example assumes the Tcl event loop is running which is required for receiving notifications.)

 1: % proc pargs args {puts "Device event: [join $args ,]"}
 2: % set notifier [twapi::start_device_notifier pargs -deviceinterface volume]
 3: devnotifier#2
 4: Device event: devnotifier#2,devnodes_changed
 5: Device event: devnotifier#2,devnodes_changed
 6: Device event: devnotifier#2,devicearrival,volume,E:,
 7: Device event: devnotifier#2,devnodes_changed
 8: Device event: devnotifier#2,deviceremovecomplete,volume,E:,
 9: Device event: devnotifier#2,devnodes_changed
10: Device event: devnotifier#2,deviceremovecomplete,volume,D:,mediachange
11: Device event: devnotifier#2,devicearrival,volume,D:,mediachange
12: % ::twapi::stop_device_notifier $notifier

The twapi::start_device_notifier command on Line 2 is used to receive notifications of new volumes including USB pen drives, CD insertion and network shares. It invokes the supplied callback whenever a device volume change event occurs. The callback can filter for the events of interest based on the parameter supplied to it. For example, the above console session shows the insertion and removal of a USB pen drive (Lines 6 and 8) followed by the removal and insertion of a new CD (Lines 10 and 11). The mediachange attribute indicates that the event is only a change of CD media as opposed to a new CD-ROM device.

7.6 How can I access Microsoft structured storage?

The tclstorage extension provides access to Microsoft's structured storage format.

8 Windows Shell and Desktop

8.1 How can I create desktop shortcuts?

Use the write_shortcut command of the TWAPI extension to create shortcuts. The code below will create a shortcut on the desktop to notepad.exe.

1: % set path [file join [::twapi::get_shell_folder desktopdirectory]
2: % twapi::write_shortcut $path -path c:/windows/system32/notepad.exe

For URL shortcuts, use the write_url_shortcut command from TWAPI.

8.2 How can I register a hotkey to invoke a script?

Windows hotkeys are a means to invoke actions in an application irrespective of which application has the keyboard focus. Run the example below in a DOS window. Ctrl-Alt-F11 will start a copy of notepad no matter which application has the foreground. Ctrl-Alt-F12 will stop the script.

 1: set notepad_hk "Ctrl-Alt-F11"
 2: set exit_hk    "Ctrl-Alt-F12"
 3: puts "$notepad_hk will bring up a new copy of notepad"
 4: puts "$exit_hk will unregister the hotkey and exit"
 6: proc remove_hotkeys_and_exit {} {
 7:   twapi::unregister_hotkey $::notepad_hk_id
 8:   twapi::unregister_hotkey $::exit_hk_id
 9:   exit
10: }
12: set notepad_hk_id [twapi::register_hotkey Ctrl-Alt-F11 "exec notepad.exe &"]
13: set exit_hk_id    [twapi::register_hotkey Ctrl-Alt-F12 "remove_hotkeys_and_exit"]
15: # If running in tclsh, need a vwait to get eventloop running.
16: vwait forever

8.3 How can I copy and paste text to the clipboard?

If you are also using Tk, use the clipboard command to read and write the clipboard. If you are not using Tk, or you need a format that is not supported by the clipboard command, use the read_clipboard_text and write_clipboard_text commands from TWAPI as shown in the next entry.

8.4 How can I copy and paste formatted or binary data ?

If data you are copying and pasting is not plain text, use the read_clipboard and write_clipboard commands from TWAPI.

The example session below gets HTML format data from the clipboard.

 1: % twapi::open_clipboard (openclip)
 2: % set fmt [::twapi::register_clipboard_format "HTML Format"] (getclipfmt)
 3: 49384
 4: % twapi::read_clipboard $fmt
 5: Version:0.9
 6: StartHTML:00000158
 7: EndHTML:00000260
 8: ...lines not shown...
 9: <html><body>
10: <!--StartFragment--><h2><a name="name">Tcl for Windows FAQ</a></h2><!--EndFragment-->
11: </body>
12: </html>
13: % twapi::read_clipboard_text
14: Tcl for Windows FAQ
15: % twapi::close_clipboard

Since HTML format is not a standard predefined clipboard format, Line 2 of the example first gets the format identifier associated with it. Note also the difference in results with the read_clipboard command on Line 4 and the read_clipboard_text command on Line 13.

9 Interoperating with other applications

9.1 How can Tcl communicate with other applications using DDE?

Tcl's built-in dde package allows Tcl scripts to act as a DDE client or server. However, DDE is a legacy technology and you should use COM interfaces instead wherever possible.

9.2 How can Tcl act as a COM client?

Several extensions support COM client access from Tcl.

  • The COM module of the TWAPI extension (32- and 64-bit)
  • The TCOM extension (32-bit only, not maintained)
  • The Optcl extension (32-bit only, not maintained)

The online book chapter The Component Object Model provides a detailed guide to using the COM module from TWAPI.

9.3 How can Tcl act as a COM server?

All of the above packages can be used to implement COM components.

9.4 How can I automate Internet Explorer with Tcl?

Automation of IE using COM is done by creating an instance using the PROGID InternetExplorer.Application and calling methods on it. You can find documentation on MSDN. Here is an example using TWAPI.

1: % set ie [twapi::comobj InternetExplorer.Application]
2: % $ie Visible true
3: % $ie Navigate
4: % $ie destroy

For a TCOM example, see the Wiki article at

9.5 How can I integrate with Microsoft Office and othe common applications?

The CAWT package provides a high level Tcl API over COM to interact with Microsoft Office and other Windows applications.

At a lower level, automation or integration with Office can be accomplished using any of the COM extensions mentioned above. For documentation on the objects and methods exposed by Office, follow the links on the Office developer page.

9.6 How can SQL Server and other databases be accessed from Tcl?

The tdbc package shipped as part of the core Tcl 8.6 distribution includes drivers for various database implementations as well as an ODBC connector. In addition to the reference pages in the Tcl documentation, an online introduction is available.

10 System Administration

10.1 How can I manage user accounts?

The TWAPI extension provides several commands related to user and group account management.

1: : % twapi::new_user brad -password jennifer
2: : % twapi::add_user_to_global_group angelina_fans brad
3: : % twapi::set_user_password brad angelina 
4: : % twapi::delete_user brad

You can also use the Active Directory interfaces for this purpose.

10.2 How can I access Active Directory with Tcl?

You can work with Active Directory via the LDAP module in the tcllib package library, or via the Active Directory Service Interface (ADSI) through one of the Tcl COM extensions.

10.3 How can I use WMI for system management?

Like ADSI, Windows Management Instrumentation (WMI) also provides a scriptable interface via COM which is documented on the MSDN WMI Reference site.

 1: % twapi::comobj_object "winmgmts://./root/cimv2"
 2: % $wmi -with {
 3:     {ExecQuery "select * from Win32_NetworkAdapter"}
 4:   } -iterate net {
 5:     puts "[$net DeviceID]:[$net Description]"
 6:     $net destroy
 7:   }
 8: 1:Broadcom 440x 10/100 Integrated Controller
 9: 3:Intel(R) PRO/Wireless 2915ABG Network Connection
10: 3:1394 Net Adapter
11: ...

The online book chapter Windows Management Instrumentation provides a detailed guide to accessing WMI from Tcl. Additional examples are on the TWAPI and WMI wiki page.

10.4 How can I check if an application or hotfix is installed?

The Windows Installer database can be accessed using either WMI or the Windows Installer COM object. Either method requires one of the Tcl COM extensions. The example below checks for a specific hotfix.

1: % set wmi [twapi::comobj_object "winmgmts://./root/cimv2"]
2: ::oo::Obj1233
3: % $wmi -with {
4:     {ExecQuery "select * from Win32_QuickFixEngineering where HotFixID='KB2485663'"}
5:   } -iterate app {
6:     puts "[$app HotFixID]: [$app Description]"
7:   }
8: KB2485663: Security Update for Windows XP (KB2485663)

10.5 How can I read and write the event log?

Use the Windows event log module from the TWAPI extension. Here is an example to dump the Application event log to the console:

 1:  set hevl [twapi::eventlog_open -source Application]
 2:  # Make translation binary (lf), since records have embedded CR-LF,
 3:  # we will have to explicitly output CR-LF pairs
 4:  fconfigure stdout -translation lf
 5:  # Keep reading record until no more
 6:  while {[llength [set events [twapi::eventlog_read $hevl]]]} {
 7:    # print out each record
 8:    foreach eventrec $events {
 9:      array set event $eventrec
10:      set time [clock format $event(-timewritten) -format "%x %X"]
11:      set source   $event(-source)
12:      set category [twapi::eventlog_format_category $eventrec -width -1]
13:      set message  [twapi::eventlog_format_message $eventrec -width -1]
14:      puts -nonewline "Time: $time\r\nSource: $source\r\nCategory: $category\r\n$message\r\n\r\n"
15:    }
16:  }
17: twapi::eventlog_close $hevl

11 Interoperability with .Net

11.1 Is there a .NET version of Tcl?

Eagle is an implementation of the Tcl scripting language for the .Net Common Language Runtime (CLR). It is fully interoperable with other .Net languages and components.

11.2 How can I call .NET components from Tcl?

The Garuda extension provides support for calling .Net components from Tcl.

12 Networking and Communications

12.1 How can I communicate over the network?

The Tcl socket command creates a TCP/IP socket that can be used with the standard Tcl I/O commands such as read and puts. The iocp_inet package provides a much higher performance implementation of the same.

12.2 How can I communicate over named pipes and why would I want to?

Use TWAPI's namedpipe_server or namedpipe_client commands. These create a Tcl channel that can be used with the standard Tcl I/O commands. Named pipes are not advised over wide area network connections for performance reasons. In local environments, their primary benefit is that they provide an easy means for access control and authentication.

12.3 How can I communicate over serial ports?

Tcl's open command can be used to open a serial port. For example,

set fd [open "COM1:" r+]

For ports with number greater than 9, the UNC syntax must be used instead, for example \\.\COM10.

set fd [open "\\\\.\\COM10" r+]

Note the \ is doubled in the command as it is the escape character in Tcl syntax.

Once open, the standard Tcl I/O commands can be used to read and write to the port.

12.4 How can I download a file or a Web page?

Tcl comes with a standard package http

 1: % package require http
 2: 2.8.3
 3: % set tok [http::geturl]
 4: ::http::1
 5: % puts "Status: [http::status $tok]"
 6: Status: ok
 7: % if {[http::status $tok] eq "ok"} { puts [http::data $tok] }
 8: <HTML><HEAD><meta http-equiv="content-type" content="text/html;charset=utf-8">
 9: ...more lines...
10: </HTML>
11: % http::cleanup $tok

Packages for other protocols, like FTP, are available in tcllib.

The TclCurl extension provides an interface to the libcurl library for many more protocols and options.

12.5 How do I secure my connections with SSL/TLS?

You have the option of using the TLS extension or the tls_socket command from the TWAPI extension. The latter integrates with the Windows certificate store.

13 Security

13.1 How do I control access to a file or other resource?

The twapi_security module in the TWAPI extension implements a complete set of commands for manipulating access control lists for files and other resources. The Access Control section in the online book chapter Windows Security describes use of these commands.

Alternatively, you can also use the Tcl `exec` command to run the cacls.exe program that is included with Windows passing it appropriate parameters.

13.2 How do I manage certificates?

The pki module in tcllib provides portable commands for certificate creation and validation. The twapi_crypto module in the TWAPI extension also provides similar functionality as well integration with the Windows certificate store. The primary advantage of the integration is automatic updates of root certificates and revocation lists.

14 Building Tcl for Windows

14.1 Where can I get the Tcl source code?

The source code for the public releases of Tcl can be obtained from the SourceForge Tcl download area at Extract the zip file to wherever you want to do the build. Depending on the tool chain you will use to build Tcl, it is advisable to not have spaces in the path.

To get the current development snapshot of Tcl, you can check out sources from the Tcl source repository at with a mirror at It is maintained using a distributed revision control system called fossil, binaries for which can be downloaded from Detailed instructions for working with the Tcl repository are at

Note: Do not place the sources in a path that has spaces in it. Some of the compiler tools have problems with such paths. If necessary, you can use the DOS subst command to assign a drive letter to the path in order to hide the spaces.

14.2 Which compiler should I use to build Tcl ?

There are several tool chain options for building Tcl for Windows.

  • Building with Visual C++ 6.0, as opposed to a newer Visual Studio version, has the advantage that the associated runtime library msvcrt.dll is pre-installed on every Windows system and does not have to be shipped with your Tcl distribution. However, the compiler is not free.
  • Building with the Microsoft SDK compilers requires that the compiler runtimes be redistributed. But the compilers themselves are free.
  • Building with the open source MinGW tool chain based on gcc also does not require redistributing runtime libraries as it uses msvcrt.dll. Setup is a little more complicated.
  • The compilers in newer versions of Visual Studio are identical to the free SDK compilers so not much is to be gained from using these commercial versions.

For multi-platform builds, the BAWT toolchain provides a complete self-contained environment for building Tcl/Tk along with almost all extensions.

14.3 How do I build Tcl using Visual C++?

The file win\ in the win directory is used to build Tcl using Microsoft's compilers. The build process automatically figures out what version of the compiler is being used.

Note Visual C++ 6.0 can only build the 32 bit version of Tcl.

There are several options that can be passed to See the top of the file for instructions. The sample below illustrates most common usage.

"%ProgramFiles%\Microsoft Visual Studio\VC98\Bin\vcvars32.bat"
nmake -f INSTALLDIR=c:\tcl release
nmake -f INSTALLDIR=c:\tcl install

The last step is only necessary to install the binaries on the build system or to create a distribution.

Note this only builds Tcl, and not the Tk library. If you want to build the Tk library as well, you need the February 2003 version of the SDK since Visual C++ 6.0 does not contain the required libraries for theming support. Later versions of the SDK will not do as they are not compatible with Visual C++ 6.0. The environment has to be set up so that the SDK headers and libraries appear before the Visual C++ ones. The following assumes the Tcl and Tk distributions are side-by-side in directories called tcl and tk.

1: "%ProgramFiles%\Microsoft Visual Studio\VC98\Bin\vcvars32.bat"
2: "c:\src\SDK-Feb-2003\setenv" /XP32 /RETAIL
4: nmake -f INSTALLDIR=c:\tcl release
5: nmake -f INSTALLDIR=c:\tcl install
6: nmake -f TCLDIR=..\..\tcl INSTALLDIR=c:\tcl release
7: nmake -f TCLDIR=..\..\tcl INSTALLDIR=c:\tcl install

Building with newer compilers is no different except for the path to the appropriate vcvars batch file.

15 Tcl packages and extensions

15.1 Tcllib

Tcllib is a collection of cross-platform Tcl packages that cover a large number of areas from text processing, mathematical algorithms, data structures, parsing, data structures, HTML and XML, networking, automata and more. It is available from

15.2 Tcl for Windows API (TWAPI)

The TWAPI extension includes modules that cover a broad cross-section of the Windows API. It is available at

15.3 TCOM

The TCOM extension provides support for both COM client and server access from Tcl. It is available from Although stable, it is not under active development and there is no 64-bit version available.

15.4 Optcl

The Optcl extension supports COM client and server access and also support for hosting ActiveX controls. It is available at Like TCOM, it is not under active development and no 64-bit version is available.

15.5 CAWT

The CAWT (COM Automation With Tcl) package (formerly TcomOffice) provides high level interfaces to Microsoft Office (Excel, Word, Powerpoint), Internet Explorer, Matlab and Google Earth. It is available at

15.6 TkPrint

The TkPrint extension provides commands for printing. It is available at

15.7 Gdi and Printer

The Gdi and Printer extensions contain commands to interface to the Win32 GDI and printing API's.

15.8 Eagle and Garuda

Eagle is an implementation of Tcl for .Net. Garuda is a Tcl extension that supports calling .Net components from Tcl. Both are available from

15.9 TclCurl

The TclCurl extension provides a Tcl-callable interface to the libcurl library for retrieving URL's using many different protocols. It is available from

15.10 tclkit

Tclkit is a single-file Tcl executable that also supports binding of application scripts within the executable to allow single-file distribution of applications that can be run directly without installing or unpacking. See

15.11 freewrap

Freewrap is another single-executable distribution option. It is available from