Comparisons in a shell script may either be accomplished using regular operators (such as <, > or =) or using the equivalent (-lt, -gt, -eq) for POSIX shells.

if statements take the form

if [[ condition ]]
then
	do this
elif [[ condition ]]
then
	do this instead
else
	do this by default
fi

Note the spacing on the conditionals. There must be a space between the brackets and their contents, e.g.

if [[ $a < $b ]]

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