2008-03-28 [Sarnold]: I wanted a cron task to make backups of an important file, and be able to simply restore or examine a backup.
The following script is just to be invoked every 3 minutes (or more if you want) by calling `autosave /path/to/myfile`.

It creates a directory `_SAVE` and subdirectories named after the date (%Y%m%d) which contain indexed backups. 
Just see the listing:
======
- myprecious.gnumeric
+ _SAVE
|- myprecious.gnumeric
|-+ 20080320
 |- 1_myprecious.gnumeric
 |- 2_myprecious.gnumeric
|-+ 20080321
 |- 1_myprecious.gnumeric
======
----
''autosave source code''
======
#!/usr/bin/env tclsh

proc mkdir {dir name} {
	if {![file isdirectory $dir/$name]} {
		file mkdir $dir/$name
	}
	return $dir/$name
}

proc save {file dir} {
	set date [clock format [clock seconds] -format "%Y%m%d"]
	set dir [mkdir $dir $date]
	set index 0
	while {[file exists $dir/[incr index]_$file]} {}
	file copy $file $dir/${index}_$file
}

proc main {file} {
	set dir [file dirname [file normalize $file]]
	cd $dir
	set file [file tail $file]
	set save [mkdir $dir _SAVE]
	if {![file exists $save/$file]} {
		file copy $file $save/$file
		save $file $save
	} elseif {[file mtime $file] > [file mtime $save/$file]} {
		file copy -force $file $save/$file
		save $file $save
	}
}
======
----
!!!!!!
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!!!!!!