Version 22 of string trim

string trim removes characters from the beginning and end of a string.

Synopsis

: string trim string ?chars?

Description

Returns a value equal to string except that any leading or trailing characters that occur in chars are removed.
If chars is not specified then white space is removed (spaces, tabs, newlines, and carriage returns).

Examples

# http://ideone.com/IX2f6Y
set s1 { Hello }
set s2 [string trim $s1]
puts "<$s1> <$s2>"

set s1 {*** Hello_###}
set s2 [string trim $s1 *#_]
puts "<$s1> <$s2>"

Output:

< Hello > <Hello>
<*** Hello_###> < Hello>

# http://codepad.org/b4bHNWjo
set s1 { * Hello ** }
set s2 [string trim $s1]
set s3 [string trim $s1 { *}]
puts <$s1>\n<$s2>\n<$s3>

Output:

< * Hello ** >
<* Hello **>
<Hello>

What Constitutes Whitespace

See TIP #318: Extend Default Whitespace in 'string trim' Beyond ASCII .

escargo 2008-06-02: This also related to behavior discussed in comp.lang.tcl with the subject, "string trim not trimming special space characters" (starting on 2008-03-04).

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.

LV: You could either update the TIP page with your concerns, or post a comment over on the TCT mailing list.

Discussion

MiHa 2015-05-17: As I already ranted, missing examples are a common shortcoming in the docs. As an example, how I would like examples done (here in the wiki, as well as in the help-system that comes with the tcl/tk-installation, I added a demo-section, with links to two different online-compilers, where the examples can be seen "live".

pyk 2015-05-17: The added examples are better than what previously passed as examples on this page. I've adjusted them to conform to the Tcl minimal escaping style. MiHa, if you as the author of the new examples take exception to that, just change them back to your own preferred style. As far as putting the Description section before the Synopsis section, I think there's enough precedent having an unnamed summary with the description coming after the synopsis to justify leaving the current order as it is.

Category Command

Category String Processing