Condition tests using the if/then construct may be nested. The net result is equivalent to using the && compound comparison operator.

a=3

if [ "$a" -gt 0 ]
then
  if [ "$a" -lt 5 ]
  then
    echo "The value of \"a\" lies somewhere between 0 and 5."
  fi
fi

# Same result as:

if [ "$a" -gt 0 ] && [ "$a" -lt 5 ]
then
  echo "The value of \"a\" lies somewhere between 0 and 5."
fi

Example 37.4, “Using arrays and other miscellaneous trickery to deal four random hands from a deck of cards” and Example 17.11, “Backlight: changes the brightness of the (laptop) screen backlight” demonstrate nested if/then condition tests.