bc:tldr:c5533

The command bc --expression='${5 - 3}' is using the bc command-line calculator with a specific mathematical expression as an argument.

• bc is a command-line calculator that allows you to perform mathematical calculations.
• --expression is an option or flag for bc that indicates that the following argument is a mathematical expression to be calculated.
• '${5 - 3}' is the mathematical expression itself enclosed in single quotes.

In this specific expression, ${5 - 3}, we have a subtraction operation.

• ${} is a Bash shell syntax used for parameter expansion or substitution. It allows you to access the value of a specific bash parameter or variable.
• 5 and 3 are the values being subtracted.

So, when you execute this command, bc will perform the calculation of 5 - 3, which equals 2. The result 2 will be printed on the terminal output.