On 23/08/2012 17:09, gene golub wrote:
Hello forum
I was wondering if somebody could explain what is the difference in use of the
above within 'if' statement.
Is one superseds the other so I can use just one without ever considering the
other.
Sample:
If [ -d somedir ];then
...
Hello Gene,
Double brackets implicitly quote all arguments, so you don't need to add quotes
yourself.
If a="fee fie foe fum", then the expression [[ -f $a ]]
would be equivalent to [ -f "$a" ].
(The single '[' is effectively an alias for the builtin 'test', and ignores any
trailing ']' character).
There is at least special case where quoting still makes
a difference inside double brackets: pattern matching.
[[ $a == fee* ]] would test true for all strings $a starting with "fee".
[[ $a == "fee*" ]] would expect $a to contain the literal four character string
"fee*"
Regards,
Henk
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