G'day Wiggins,

"I searched for the program '[[', but none was found."

It's part of the shell syntax (see the bash manpage). It's used in conjunction with ']]'. Both are reserved words. Searching in the manpage finds, among others: 

RESERVED WORDS
       ... The following  words  are  recognized  as  reserved ...  [[
+ ]]

[download]

and, later

SHELL GRAMMAR
    ...
        [[ expression ]]
              ... the evaluation of the  conditional  expression  expr
+ession. ...
              ...

[download]

— Ken

In reply to Re: Back-ticks and bash by kcott
in thread Back-ticks and bash by Wiggins

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