Purpose: often one needs to know something about the system on which the application is running to ''do the right thing''.  Here are some ways to get info.
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Here's a simple Tcl script which outputs a number of pieces of information:

 #! /usr/tcl84/bin/tclsh
 puts "This is Tcl version $tcl_version , patchlevel $tcl_patchLevel"
 puts "[info nameofexecutable] is [info tclversion] patch [info patchlevel]"
 puts "Directory(s) where package require will search:"
 puts "$auto_path"
 puts "tcl_libPath = $tcl_libPath"  ;# May want to skip this one
 puts "tcl_pkgPath = $tcl_pkgPath"  ;# May want to skip this one
 puts "tcl_library = $tcl_library"
 puts "info library = [info library]"
 puts "Shared libraries are expected to use the extension [info sharedlibextension]"
 puts "platform information:"
 parray tcl_platform

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A good start is to look at what version of Tcl you've got:
 info patchlevel
Then look at the contents of the tcl_platform global array:
 parray tcl_platform

See [tcl_platform] for a list of the output of this command on various systems.

See [info library] for the location where tcl's core libraries are installed.
See the variable $[auto_path] for a list of directories where tcl will search for extensions.
See the variable $[tcl_pkgPath] for a list of directories where some versions of tcl seek [[...]]
See [tcl_libPath] for [[what??]].

Now, if you are running Unix, you can obtain additional machine configuration information by running:
 exec uname -a
And for Solaris users, you can find out your processor speed using the following ''magic incantation'':
 exec psrinfo -v
(the executable is located in ''/usr/sbin'' on this machine at least... :^)

On Linux, you can work out your basic memory usage profile using:
 exec free

Unix systems with the luxury of a SYSV ps (like both IRIX and Solaris) can use it to discover useful info about the Tcl process itself:
 exec /bin/ps -p [pid] -o {pid sz rss util pcpu time etime comm}
And there is also ''sysconf'' which is exposed on IRIX systems but not Solaris AFAICT...
 exec sysconf
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Actually, solaris has sysinfo, but it's not all that useful ;^)

I am rather partial to:

   set name xterm
   exec /bin/ps -Ao fname,pid,pcpu,pmem,vsz,rss,etime | grep $name
'''-PSE'''
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See [Measuring your Application's CPU Utilization] for a related discussion.
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Please extend this page with goodies and snippets from other OSes that I know less well!  '''DKF'''

For all versions of Windows, download applications from:
[http://hp.vector.co.jp/authors/VA002374/src/download.html]

For Windows NT 4.0 and up, the [TWAPI] commands get_os_info, get_memory_info, get_network_info and get_processor_info will provide various types of system information.


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[CL] maintains an exhausting, if not exhaustive, list of ways to calculate
memory characteristics under various Unix flavors at
[http://phaseit.net/claird/comp.unix.admin/admin.html#memory].
Several of these commands give configuration information beyond memory.

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