bc:tldr:7e4fd

This command uses the echo and bc tools in the terminal to perform a mathematical calculation.

Here's a breakdown of the command:

1. echo: This command is used to display a line of text or the value of a variable. In this case, it displays the line of text '${select}(${1})'.

2. '${select}(${1})': This is the text being echoed. It contains two components within single quotes:

   a. '${select}': This is a placeholder for a variable or function. It represents an unknown value that will be replaced by an actual value or expression later.

   b. '(${1})': This is another placeholder, but it specifically represents the first command line argument passed to this script or command.

3. |: This is called a pipe symbol. It is used to redirect the output of one command to another command. In this case, it pipes the output of echo to the input of bc command.

4. bc: This is the basic calculator command. It is used for mathematical calculations in the terminal.

5. --mathlib: This is an option passed to the bc command. It ensures that the mathematical functions and constants library is loaded, allowing the use of functions like sine, cosine, etc.

Overall, this command takes a value provided as the first command line argument (denoted by ${1}), substitutes it into the text '${select}(${1})', and then passes the resulting expression to bc for evaluation using mathematical functions.