The [exec] command treats ampersands (&) in its arguments specially, e.g. for making execution asynchronous. This can be a problem if an argument, like an URL, contains ampersamds.

petterik@gol.com (Petteri K) writes in [the comp.lang.tcl newsgroup]:

 Would anybody know a workaround in case $url contains
 character '&' e.g. 
 http://127.0.0.1/cgi-bin/script?var1=abc&var2=xyz
[Benjamin Riefenstahl] replied:
[exec] plays tricks with quoting which make it impossible for me to
get the right command executed in Tcl 8.3.4.  What works on W2K here
though is this:

----
   set url "http://www.tcl.tk?hello&hi"
   set shell [open "|[file join $env(COMSPEC)]" w]
   fconfigure $shell -buffering line
   puts $shell "start \"\" \"$url\""
   puts $shell exit
   close $shell

I hope this works on Windows 9x/Me, too.

----

Here is the simplest way that I've found, and I use it in my mindweb [http://www.rohanpall.com/mindweb/].  It relies on the [rundll] utility available with some versions of Windows.

  proc goUrl x {
    global tcl_platform
    if {$tcl_platform(platform) eq "windows"} {
      set x [regsub -all -nocase {htm} $x {ht%6D}]
      exec rundll32 url.dll,FileProtocolHandler $x &
    }
  } ;# This definitely works on Win95 and Win98. 
  
See [invoking browsers] ''--[Ro]''

----

For Unix/Linux, it is highly probable that the line
   set shell [open "|/bin/sh" w]
works as well (just in place of the "start" command, you'd have to substitute a more specific one...)

But one idea for more cross-platformity: Unix has (guaranteed?) env(SHELL) to give the default shell; Windows has env(COMSPEC), Mac I don't know. Would it be worthwile to unify these into a, say, ''::[tcl_platform](shell)'' element? ([RS])