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It seems that you can write a negated conditional either as
if ! [[ ... ]]; then
or
if [[ ! ... ]]; then
Are there reasons to choose one or the other approach, assuming that the semantics of the operation are the same? (I.e., obviously, in the second version, if the ... is a compound statement and you're not careful to group the expression properly then you may end up negating only the first part of the expression.)
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Include full stops/exclamation marks/question marks/quotation marks before the close bracket only if the complete sentence/quote is in brackets. Otherwise, punctuate after the closing bracket.
Bash maintains the history of the commands executed in the current session. We can use the exclamation mark (!) to execute specific commands from the history.
While comparing variables in Bash, we generally use single brackets ([ ]) and double brackets ([[ ]]) interchangeably. For example, we can use the expressions [ 3 -eq 3 ] or [[ 3 -eq 3 ]] while checking whether 3 is equal to 3. Both will be successful in performing the comparison.
In addition to using single quotes for exclamations, in most shells you can also use a backslash \ to escape it. That is: git commit -m "Frustrating <insert object of frustration here>\!"
No, it is completely up to your own preference. The next commands are completely equivalent:
if [[ $x -ne $y ]]; then
if ! [[ $x -eq $y ]]; then
if [[ ! $x -eq $y ]]; then
Your preferences might be based on different if conditions:
if [[ $x -ne $y ]]; then: Simple comparisons without any complexity like ordinary variable comparison.if ! [[ $x -eq $y ]]; then: Suppose you have a complex if condition that might be a result of some function instead of $x -eq $y.if [[ ! $x -eq $y ]]; then: Unnecessary, use either first or second, depending on what type of if condition you have. I would never use this one!
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