Mastering Bash

Test operators (?)

The test operator can be used in a few different scenarios. We already saw in the parameter substitution that it is used to check whether a variable has a value or not. In arithmetic operations, it can be used to implement the trinary or ternary operator in a C-style notation:

#!/bin/bashx=20y=30w=40z=50k=100echo 'Usually you would write a control loop in the following way:'echo 'if [[ $x -gt $y ]]'echo '     then'echo '       z="$w"'echo '       echo "The value for z is: $z"'echo '     else'echo '       z="$k"'echo ' echo "The value for z is: $z"'echo 'fi'if [[ $x -gt $y ]]   then      z="$w"      echo "The value for z is: $z"   else      z="$k"      echo "The value for z is: $z"fiecho 'But you can also use the C-style trinary operator to achieve the same result:'echo ...