The 'Hello World' of shell scripting, and the command you reach for whenever you need to check a variable's value?

echo simply prints whatever text follows it back to the screen, making it the shell scripting equivalent of a 'Hello World' first exercise, and also a constant, practical debugging tool. Typing echo $PATH, for example, reveals the current value of that variable, and sprinkling echo statements throughout a script lets you narrate its progress and check what's happening at each step.

'yell' and 'sing' are simply playful, unrelated words chosen to rhyme thematically with 'echo,' but neither is an actual command with any function in a shell.

Despite being one of the simplest possible commands, echo remains a lifelong habit for developers, since checking a variable's value or confirming a script reached a certain point is something programmers do constantly, no matter how experienced they become.