esac

View documentation for the case keyword

$ tldr case

esac

The `esac` command in Linux is not actually a standalone command. It serves as the closing statement for a `case` statement within shell scripts.

A `case` statement allows for conditional execution of different code blocks based on the value of a variable. `case` provides a structured alternative to nested `if-then-else` statements, especially when dealing with multiple possible values. The `case` statement begins with the `case` keyword and concludes with `esac` (case spelled backwards).

Without `esac`, the shell interpreter would not know where the `case` statement ends, leading to syntax errors and unpredictable script behavior. `esac` essentially signals the end of the pattern matching and associated actions defined within the `case` construct. Using `esac` ensures the shell correctly parses and executes the intended logic based on the variable's value and the defined patterns.

`esac` is not a standalone command and will generate an error if used outside of a `case` statement. It only serves to terminate the `case` block.

Simple Example:
#!/bin/bash
read -p "Enter a color (red, green, blue): " color
case $color in
red) echo "You chose red." ;;
green) echo "You chose green." ;;
blue) echo "You chose blue." ;;
*) echo "Invalid color choice." ;;
esac

This script prompts the user to enter a color, then uses a `case` statement to determine the action based on the input. The `esac` statement marks the end of the `case` block.

case(1), if(1), then(1), else(1), elif(1), fi(1)