Purpose: Show how to create a temp file.

DL
----

Tcl doesn't have a built-in command to create a temporary file and there are no built-in variables for temp directories, so you have to do a little work.

Best is to figure out the temp directory separately.  Then you can create multiple files in it.

 switch $tcl_platform(platform) {
    unix {
	set tmpdir /tmp   # or even $::env(TMPDIR), at times.
    } macintosh {
	set tmpdir $env(TRASH_FOLDER)  ;# a better place?
    } default {
	set tmpdir [pwd]
	catch {set tmpdir $env(TMP)}
	catch {set tmpdir $env(TEMP)}
    }
 }

If you just want one temp file:

 set filename [file join $tmpdir [pid]]

If you want multiple tmpfiles, consider appending things like the application name, counter, time stamp, etc.  For example:

 set file [file join $tmpdir $appname.[pid].[incr ::globalCounter]]

''DKF'' - Or create in a subdirectory/subfolder

 if {![file exists [file join $tmpdir [pid]]]} {
    file mkdir [file join $tmpdir [pid]]
 }
 set file [file join $tmpdir [pid] [incr ::globalCounter]]

''[Michael Schlenker]'' - Be aware of potential race conditions while opening temp files. The linux secure programming howto has some nice examples for the linux platform:
http://www.linuxdoc.org/HOWTO/Secure-Programs-HOWTO/avoid-race.html

To be sure to get a new tempfile (and not some evil symlink) try something like:

 set access [list RDWR CREAT EXCL TRUNC]
 set perm 0600
 if {[catch {open $file $access $perm} fid ]} {
     # something went wrong 
     error "Could not open tempfile."
 } 
 # ok everything went well