In the course of making Playtree, I came across some esoteric terminal commands for MacOS. To start with the least useful:
afplay <audio_file>
will play a specified audio file from the command line. I used this in an early CLI prototype for Playtree, but its utility is pretty limited. There’s no way to control audio once playback starts. You can stop playback by sending an interrupt signal with CTRL-C, and you can “mute” audio by suspending the process with CTRL-Z. This doesn’t pause playback, though. It’s still playing through silently in the background.
There are few command line options, though. You can set the volume and the time to play before ending playback.You can set the playback rate, too. It’s a fun old command buried in the OS. There’s potential, here, to pull a prank on a friend, if only people still had audio files on hand. Maybe the say command, which reads the input text aloud, would suffice.
Make sure to check out the afinfo and afconvert commands, which I haven’t tried but might actually be useful!
You probably already use the next pair of commands all the time, just not on the command line. They are pbcopy and pbpaste, available on MacOS.
pbcopy copies stdin to the clipboard, and pbpaste outputs the clipboard to stdout. For example:
echo 'This is a sentence' | pbcopy
will copy This is a sentence to the clipboard. This can be useful if you need to copy the contents of a file, for instance:
cat file.txt | pbcopy
Similarly, you can paste the clipboard to a file:
pbpaste > new_file.txt
pbpaste >> file_to_append_to.txt
I found these commands pretty useful when I needed to interface between my browser and my terminal. The easiest way to get text from the browser is to copy it, and often the easiest way to interact with the local filesystem is via the command line.
Another feature of pbcopy and pbpaste is that you can target one of four clipboards with the -pboard flag. I didn’t end up using this feature very often, since I was almost always using these commands in conjunction with normal copy and paste, but maybe you can make good use of it.
The last tidbit is a misnomer on two counts—it isn’t exclusive to MacOS, and the takeaway isn’t about the command itself! The command is less. You can use less to make terminal output more human readable. It’ll take an input stream and display only a fraction of the stream at a time. You can move within the stream using the arrow keys and by entering commands.
You may already know about less. What you may not know is that less outputs the stream it’s reading to stdout! This means that you can do something like
echo "This is some text to read" | less | cat
and, instead of seeing the text in less, it will just be printed to the terminal.
Why would you ever want to do that? Isn’t it redundant? The main benefit is that other commands may utilize less to display their output. git diff works this way. While working on Playtree, I’d often pepper the code with debugger and console.log statements. Before committing my code, I’d check the diff to see if I’d left any stragglers around. I realized you can just pipe git diff to grep, and it was much faster than sifting through the diff in less:
git diff | grep console.log
You can even pipe the output of grep back to less:
git diff | grep console.log | less
This made it much easier to sift through diffs if I needed to. Granted, there’s a lot I’ve yet to learn about how to move around a file quickly in less itself. I’ll probably get to that when I get around to vim.
That’s all I’ve got for now. Check out this reference for other available MacOS commands. This index is where I found out about the ones I shared with you.