Redirecting Input and Output with File Descriptors

The history command

Let’s take a look at how the history command works and how we can use its output. When we execute the history command, the program’s output is displayed on the screen. The history command writes its output to standard output, and standard output is mapped to our terminal screen by default.

We’ve already used > and >> to redirect a program’s output to a file. For example, we can save the contents of our shell history to a file:

$ history > commands.txt

We also know that using >> appends text to an existing file. For example, we can append today’s date to the file we just created:

$ date >> commands.txt

To refresh our knowledge of these concepts, let’s try these commands in the terminal below.