'''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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''See also:''
   * TIP #318: Extend Default Whitespace in 'string trim' Beyond ASCII[http://www.tcl.tk/cgi-bin/tct/tip/318.html]

''[escargo] 2 Jun 2008'' -
This also related to behavior discussed in comp.lang.tcl with the subject,
"string trim not trimming special space characters" (starting on 4 March 2008).

The characters removed by [[string trim ''string'']] (with no ''chars'' argument) are '''not'''
all the ones for which [[string is space ''char'']] returns 1.

I think the tip should also include Unicode nonbreaking spaces.

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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]
   * [string map] replaces substrings in a string ([felipel])

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