![]() ![]() They're still available, though, because they're built into Bash, and Bash is what you're running. Which: no cd in (/usr/local/bin:/usr/bin:/bin: Built-in commands don't show up when you search for them because they don't exist in your usual executable path: $ which bash ![]() Most built-in commands are specific to Bash scripting or low-level environment settings, but a few are universally useful, such as cd (for change directory). To find out where any command is located on your system, Bash included, you can use the which command in a terminal: $ which bashĪ few commands are built into Bash. If the command does exist, then Bash executes it.īash is also a command, and it's usually the default command executed when you open a terminal window or log into a text console. When you issue a command to Bash, it searches specific directories on your system to see whether such a command exists. By nature, Bash doesn't know these commands any more than you naturally know Klingonese, but just as you can look up Klingon words, Bash can look up commands. On Linux and Unix (such as BSD and macOS), most commands are stored by default in system directories like /usr/bin and /bin. Without knowing commands, there's not much you can do with Bash. You can learn Bash, but only in the context of learning the operating system that it's running on. It's important to understand that they're two separate things: Bash is just an application, and its primary job is to run other applications (in the form of commands) that are installed on the same system. That conflates the Bash shell with the commands you type into the shell. This probably comes across as unfriendly, but it's actually a perfectly succinct representation of the many connotations around the term "Bash." To many new users, there's no separation between the concept of Bash and the concept of Linux or Unix: it's the proverbial black-screen-with-green-text into which you're supposed to code what your computer does next. Of course, knowing what you're supposed to type is another matter entirely. A prompt is a symbol, usually a dollar sign ( $), indicating that the shell is waiting for your input. ![]() When you start a terminal (such as the GNOME Terminal or Konsole on Linux or iTerm2 on macOS) running the Bash shell, you're greeted with a prompt. Of all the shells available, Bash is one of the most popular, the most powerful, and the most friendly. It was an exciting development at a time when people were feeding punchcards into computers to tell them what to do. If this was all computers did, they'd be about as interesting as a convection oven.Ĭomputer scientists recognized this early on, so they developed a shell for Unix computers that operates outside of the kernel (or around the kernel, like a shell in nature) and allows humans to interact with the computer whenever they want to. A computer's most basic set of instructions simply keeps it powered on and in a safe state: activating fans periodically to prevent overheating, using subsystems to monitor disk space or "listen" for newly attached devices, and so on. When a computer boots up, a kernel (whether it's Linux, BSD, Mach, or NT) recognizes all the physical hardware and enables each component to talk with one another and be orchestrated by some basic software. ![]()
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