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. For example:

 # This is the right way to do it.
 set mylist {a b c}
 # LV writes: technically, _this_ is the right way to do it, at least
 #  for cases more complex than a simple a, b, and c...
 # set mylist [list 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

This is one of those places where [Tcl]'s treatment of ''bareword literals''
can be frustrating to someone. 

In the second case above, Tcl considers the argument to llength a list.
Therefore, it is going to return the length of the list, which is
equivalent to this list:

        llength [list "mylist"]

[DKF]: The phrase "bareword literals" indicates a deviation from the '''[Tcl] Way'''; the concept does not really operate usefully in Tcl, unlike in a number of other languages (*cough*Perl*cough*).  The '''llength''' command always works with list values, and lists are always values. If you've a list in a variable, you need to get the list out of the variable to work out its length.

[LV]: Technically, the problem the original writer hit isn't ''Tcl'' (as an interpreter", by llength.  The documentation clearly indicates that llength takes a '''list''' as its argument. When llength looks at its argument, it sees the string ''mylist'' , which is a list - a single entry list. It sees the same way in each of these cases:

 llength mylist
 llength "mylist"
 llength {mylist}
 llength [list mylist]

In each of these cases, llength sees the list/string "mylist" and NOT the value of the string.

The problem here is that some of the Tcl l* commands expect the ''name'' of a variable, while others expect the ''value'' of a variable. And it is up to the developer to keep straight the two types of requirements.


[GWM] Note also the slightly unexpected result for:
  llength "a b c"  ;# returns 3 as the string (only one string) is interpreted as a 
        list by llength, the spaces making 3 elements. 
  llength "a {b d} c"  ;# is also 3 - the inner braces make a sub-list
  llength {a {b d} c}  ;# also 3 - it is the same as above
  llength "{a {b d} c}" ;# is 1 - the braces inside the string make a sub-list

Also not the difference between braced lists and quoted in this case:
  set a {a b c}
  llength "1 2 $a 3" ;# 6 elements in the substituted list
  llength {1 2 $a 3} ;# 4 elements in the list (which does not have $a substituted)
  
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See also [list], [lappend], [lindex], [linsert], [lrange], [lreplace], [lsearch], [lsort] .
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