[Keith Vetter] 2003-09-10: Today I wanted to print a simple text from
within tcl. I thought it should be easy--it is just ''exec notepad /p myfile.txt''. 
But to do it properly turned out to be quite difficult.

I'll explain why, but the ultimate command you need to executes is this:
   exec c:/winnt/system32/cmd.exe /c start /min c:/winnt/system32/notepad /p myfile.txt

First off, you need to look in the registry and find the print command for
text files:

    package require registry
    set app [registry get {HKEY_CLASSES_ROOT\.txt} {}]
    set pcmd [registry get HKEY_CLASSES_ROOT\\$app\\shell\\print\\command {}]
      NB. pcmd => %SystemRoot%\system32\NOTEPAD.EXE /p %1

Now put our file name for ''%1''.
    set fname myfile.txt
    regsub -all {%1} $pcmd [file normalize $fname] pcmd
      NB. pcmd => %SystemRoot%\system32\NOTEPAD.EXE /p c:/temp/myfile.txt


So far so good, but now when I try to ''exec''ute it there are two problems.
First, the ''%SystemRoot%'' needs to be handled, and second, the notepad 
window flashes momentarily. Luckily, both problems can be handled by simply
using '''start /min''' to run the command.

     set command "[auto_execok start] /min $pcmd"
     exec $command &

'''WRONG''' -- this needs to be broken into words with ''eval''

     eval exec $command &

'''WRONG''' -- the backslashes in $pcmd are doubly interpreted

     set command "[auto_execok start] /min [regsub -all {\\} $pcmd {\\\\}]"
     eval exec $command &

'''YEAH!''' (and don't try replacing the backslashes with forward slashes or
4DOS/4NT won't work)

Putting it all together, here's a short procedure 
to print a text file on windows (w/ no error checking and tested only
on Win2k):

 proc PrintText {fname} {
    package require registry
    set app [registry get {HKEY_CLASSES_ROOT\.txt} {}]
    set pcmd [registry get HKEY_CLASSES_ROOT\\$app\\shell\\print\\command {}]
    regsub -all {%1} $pcmd [file normalize $fname] pcmd
    set command "[auto_execok start] /min [regsub -all {\\} $pcmd {\\\\}]"
    eval exec $command &
 }

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This will not work on W2k, if pcmd contains spaces, and is quoted with "", as start will interpret it as the window title. (it works on Win9x). Adding a "" to the command line helps.

[KPV] could you explain your fix more. Or perhaps you could insert a dummy window title.

[HZe] I have had similar problems with the command start and the usage of quotes "". The most robust solution I found is to convert all filenames to Windows shortnames by
 set filename [file attribute $filename -shortname]
and don't include it in quotes. Otherwise I didn't get it to work on Windows NT, 2000 and XP.

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See also: [Tcl 9.0 WishList] - #66.
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[AM] [kroc] informed me about yet another utility that is available for this type of things: [http://www.pcounter.com/printraw.html]. Typical usage:

 [catch [ list exec printraw.exe [file nativename [file join $dir spoolout *.prn]] $printername ]]

[KPV] But the whole point of the above exercise was to ask the
Windows OS how to print a text file. Theorectically it should
work regardless of which utility is present or not.

[AM] I just (mis)used the page to document this utility - I could not find the other one.
I quite appreciate this insight, as I have an immediate use for it!!

[AM] Can anyone shed light on the question how to achieve this on a Macintosh? (I do not have access to one, but I am interested to know how it would work there)

[Lars H] In Mac OS X there is a Unixy command '''enscript''' which can be used for this. Probably the traditional lp/lpr can be used as well (although these may in fact be using the enscript thing to do formatting and such). On Mac OS 9 you would probably have to do something along the lines above: starting "SimpleText" (or whatever it is called in English), tell it to open a new file, tell it to insert the text you want, and then tell it to print the thing; all via AppleEvents directly (e.g. using [TclAE]) or via Applescript (the Tclapplescript extension). If the text is already in a file it might however be easier to tell the Finder to print it, as that will then call upon the proper application to do the printing.

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Category ???