'''string trim''' ''string ?chars?''

Returns a value equal to ''string'' except that any leading or trailing characters from the set given by ''chars'' are removed. I
f ''chars'' is not specified then white space is removed (spaces, tabs, newlines, and carriage returns).

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The trimleft will remove the pathname from the beginning of the string and trimright will remove the extension.  
Remember that this command will not save to a variable, therefore you must set the same or another variable:

  % set foo ../returned../
  ../returned../
  % string trim $foo ./
  returned
  % set foo
  ../returned../
  % set foo [string trim $foo ./]
  returned
  % set foo
  returned

[MG] While you can use it for filenames, the [file] command is designed specifically for working with filenames and paths. 
A more general use is to remove leading/trailing white space from a string, something like...

 (Griffiths) 9 % set foo {
 >             this is a test string    }
 
             this is a test string    
 (Griffiths) 10 % string trim $foo
 this is a test string
 
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See also:

   * [string]
   * [string trimleft]
   * [string trimright]

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