Not sure what you're asking but I did a little experiment that could answer you anyway.
In a WISH shell, I loaded a text widget:
pack [text .t]
I typed some stuff in the text using tabs:
abc def
fadlj falkm
kladsjkl;lkj lsdaf fasld
adjlk.
Between [red]abc[/red] and [red]def[/red] in the first line is a tab.
I read the contents of the text into a string:
set a [.t get 1.0 end]
I split the string into a list on linefeeds:
set alst [split $a \n]
Now the first element of the string (the first line in the text) is [red]{abc def}[/red]
I find the length of that first element:
string length [lindex $alst 0]
and the answer is [red]7[/red], meaning that the tab is a single character.
_________________
Bob Rashkin