The cat command in the example is used to find out what is in our The cat program is great for outputting file contents (its name is short for con catenate, because its purpose is to output the contents of all the files you give it, one after the other, effectively concatenating the contents in its output). We finish the example with a cat greetings.txt bash command which tells bash to run the cat program. To tell you this, it shows you its prompt again, allowing When you quit ex using the q command, the ex bash command ends and bash is ready to receive a new command. While ex is running, bash is asleep waiting for your ex session to end. After issuing this command, our prompt changed: any text we enter now is sent to ex, not to bash. Notice how in this session, we started out by giving bash the command to start the ex file editor. Hello! The "cat" program shows the contents of the file. $ cat greeting.txt And now we're back in bash! : w greeting.txt ex command to "write" the text to a file. A line with just a dot tells ex to stop inserting text. As soon as your editor exits, your bash prompt re-appears: $ ex bash command to run the "ex" program. You'll notice that while your editor is running, you are no longer at the bash prompt. When the file editor program stops running, the command ends and bash resumes operation byĪsking you for the next thing to do. While you're interacting with the file editor, bash takes a back-seat and waits for the file editor to end (which generally means you quit it). For instance, a command might start a file editor. In particular, commands that start other programs with which you can interact. Some commands can take a long time to complete, though. Will be back for the next command before you realize. For most commands, you'll barely notice this: they get executed so fast bash It is important to understand that while bash is busy with a command that you give it, you cannot interact with bash directly: you'll have to wait for it to be ready with executing its command and return to the script. We call this synchronous command execution. Your commands tell bash what you need it to do, step-by-step, command-by-command.īash generally takes one command from you at a time, executes the command, and when completed returns to you for the next command. So what are bash commands?Īt the core of the bash shell language are its commands. As a result, they create programs that can inflictĮxtensive damage to unsuspecting users and systems. There are many people that consider themselves fluent in bash but fail to understand even these most basic concepts. To get the most out of bash, and especially to avoid damage due to bash misunderstanding your intentions, it's important that you pay close attention to these basics of the bash shell language. Let's refocus on bash and start figuring out how exactly we get stuff done with it.Īs mentioned earlier, bash waits for instructions from you and then executes them to the best of its abilities. We learned a great deal about how bash and other processes work together in the terminal. What are bash commands and how do I write and issue them?
If you are interested in getting updates on the progress of this guide, you can star the source repository here. Enjoy, and let us know if you spot anything that can be improved. This chapter has reached a state of completion.
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