If you may assume the string contains at least two non-space characters, I'd write:

    /(\S.*\S)/
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which will match the first non-space character, the last non-space character, and everything in between. If you may not make the assumption, I'd modify it slightly:

    /(?=\S)(.*\S)/
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If you know the non-space characters will be letters (or digits or underscores), you can also write:

    /(\b.+\b)/
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which also works for strings containing just a single letter.