Why can I write to /dev/ttys010 using `>` but not `|`

Question

I am trying to play around and understanding ttys. In one terminal emulator window, the output of tty gives me

$ tty
/dev/ttys010

So I figured if I write to this device, the terminal window will show the output. In a second window, when I run

$ echo "test" > /dev/ttys010

The first window shows the word "test" as expect. However, when I run

$ echo "test" | /dev/ttys010

I get no output in the first window. Why is this? I assume its because | redirects stdout to programs while > redirects output to files.

Does this answer your question? What is the difference between "Redirection" and "Pipe"?. Also, you can, with echo test | sudo pipe /dev/ttyx — Pablo Bianchi, Jul 04 '23 at 15:48
With | /dev/ttys010 is NOT an executable program expecting "test" on its STDIN I/O stream, it's a device, which needs to be managed by a program. >/dev/ttys010 connects the device to the STDOUT I/O stream of the "echo" program. A better explanation is available in man bash. — waltinator, Jul 04 '23 at 16:32

score 3 · Accepted Answer · answered Jul 04 '23 at 16:18

You can write to a file with a pipe. Here are two alternatives

echo "test" | tee /dev/ttys010
echo "test" | cat > /dev/ttys010

As explained in the answer in the comment above, pipes feed stdout of one program to stdin of another program, and /dev/ttys010 is a device file, not a program and is generally not something you want to run.

Why can I write to /dev/ttys010 using `>` but not `|`

1 Answers1