How to check if a variable is empty in tcl

Question

How do you ceck if a variable is empty ? It could contain a "\n" or spaces. I am currently doing this

if {{string trimleft $var} != ""} {
   # the variable is not empty
   puts $var
 }

However the variable printed still seems to be empty ? will trimleft remove "\n" ? Is there a better approach to check if a string is empty ?

Answer 1

To answer the original question with a concern of checking for an empty line here is the corrected code example:

if {[string trim $var] != ""} {
    puts $var
}

Without specifying the ?chars? the trim will remove white space chars which are considered to be space, tab, newline and carriage return.