Quite possible, lots of people are doing it. As a small example, virtually all of the programs used in the classes I teach are platform-independent, and I run them without change on both our Windows and Linux configurations. They exercise such areas as basic Tcl functionality, file I/O, GUI management, and TCP/IP socket-based communication.
As
jerkie mentioned, some Tcl extensions aren't platform-independent, so you need to check the documentation for whichever extensions you plan to use. For example, Expect runs on Unix platforms only. But in general, an extension written in pure Tcl code only is platform independent. And there are some Windows-only extensions, jerkie, mainly providing access to Windows-specific functionality, like
registry (for obvious reasons);
dde,
tcom, and
optcl for interprocess communication;
tkprint for printing under Windows;
winico for twiddling with the icon in the Windows titlebar and installing applications in the taskbar; and
winutils for access to other Windows functionality. On the Tcl'ers Wiki (
see the page "Windows specific Tcl commands,"
for a more complete listing.
As for making sure that your application is platform independent, it's fairly easy to do in Tcl. Just be careful whenever you access the environment in any way.
[ul][li]File I/O is usually safe, as Tcl automatically translates different end-of-line conventions when it reads from a channel, and uses the platform-native convention whenever it writes to a channel.[/li]
[li]File paths are usually the biggest problem. Get in the habit of using the
file join command to construct platform-safe paths all the time, use relative pathnames when accessing other modules of your application, and read about Tcl introspection commands like
info script which returns the path of the script currently executing.[/li]
[li]Use
glob for getting directory listings instead of trying to execute the system's
ls or
dir command. Yes,
glob is rather brain-dead, IMHO, but it is Tcl-native.[/li]
[li]Similarly, use other Tcl built-ins whenever possible, like
file copy,
file delete,
file rename,
file mkdir,
cd, and
pwd.[/li]
[li]Use the Tcl
clock command for time and date manipulation.[/li]
[li]Avoid executing other programs unless absolutely necessary. This applies to both
execing another program and
opening a pipe to another program. If you do, you'll likely need to provide customized code for different platforms you support. Which brings up...[/li]
[li]To test what platform your script is running on, check the value of the predefined global
tcl_platform(platform) array element. Its value will be "macintosh", "unix", or "windows". You can then
switch based on this value to execute any platform-specific code you need to include.[/li][/ul]
Those are the basics that I can think of for writing platform-independent code. The Tcl'ers Wiki has the page "Tcl built-ins for cross platform functionality,"
providing links to more pages giving more details about these techniques.
Also, it would be a good idea to pick up TclPro and use TclPro Checker, a Tcl syntax checker. Besides being a good tool for ensuring that your script doesn't have obvious syntax errors, TclPro Checker will also raise warnings if it finds any blatant platform-dependent code in your script. You can find out more information about TclPro and download the free version from
Also, ActiveState is now offering a "quality-assured" version of TclPro, which includes updates for the latest version of Tcl, as part of its for-sale ASPN Tcl release. More information on that is available at
- Ken Jones, President
Avia Training and Consulting
866-TCL-HELP (866-825-4357) US Toll free
415-643-8692 Voice
415-643-8697 Fax
