The man page for llength is 
http://purl.org/tcl/home/man/tcl8.4/TclCmd/llength.htm

This command returns the number of [element]s in the list.  If the string is not a well-formed list, an error will be thrown.

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[caspian]: Make sure to give llength the list, not just the name variable where the list is stored.

 # This is the right way to do it.
 set mylist {a b c}
 llength $mylist

 # This is the WRONG way to do it.
 # This won't return an error, but it will always return "1",
 # no matter how long or short your list is.
 set mylist {a b c}
 llength mylist

See also [list], [lappend], [lindex], [linsert], [lrange], [lreplace], [lsearch], [lsort] .
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