Add a callback to ptyProcess.write

[lysol33]

Environment details

• OS: Linux
• OS version: 22.04
• node-pty version: v1.0.0

Issue description

I'm trying to send a response when ptyprocess gets data from PTY, but I'm having concurrency problem with overlapping requests. I think it would be a good option to add a callback to the .write() method with the data recieved from the socket

[Et7f3]

When you write the data is fully written synchronously to the pty (you can confirm it with strace).

42sh $ strace -f -e /exec,write,read node -e "
const node_pty = require('node-pty');
const pty = node_pty.spawn('/bin/sh');
pty.write('exit 123\n');
" 2>&1 | grep -e exit' 123' -e exec
execve("/nix/store/l43bdmxxlkrzwic3q24ik366qyqg3s1g-nodejs-18.16.1/bin/node", ["node", "-e", "\nconst node_pty = require('node-"...], 0x7ffd5f403928 /* 125 vars */) = 0
[pid 780469] execve("/bin/sh", ["/bin/sh"], 0x336c5d0 /* 125 vars */) = 0
[pid 780459] write(23, "exit 123\n", 9) = 9
[pid 780459] read(23, "exit 123\r\n", 65536) = 10
[pid 780469] write(2, "exit 123", 8)    = 8
[pid 780459] read(23, "exit 123\r\n", 65536) = 10
[pid 780469] write(3, "exit 123\n", 9)  = 9

node-pty/src/terminal.ts

Line 92 in d6ce76a

this._write(data);

node-pty/src/unixTerminal.ts

Lines 176 to 178 in d6ce76a

	protected _write(data: string): void {
	this._socket.write(data);
	}

It it not because data is written that the other process actually read it (it might be doing other thing)

You might have to do with echo of the tty ?

Can you provide an example where you have issue ?

[lysol33]

What I need is a way to tell when the TTY driver copies data back to the PTY master I guess. Basically, I don't need the echo of what the user writes to the process, but a signal when a data stream going back to the pty master has ended for the given input. Could this be possible?

[Et7f3]

In a deleted exemple you spawned a shell and launched ls ? Why not using node:child_process or node-pty and launch directly ls.

Here in context of a shell you can know when the process ended if you detect PS1 (you can set it to a boundary string before launching ls). We can not know when the process stopped in the general case (because it might be sleeping) and signal SIGCHLD is handled by intermediary shell.

[lysol33]

I'm not sure to be honest. I don't think I will be able to use commands such as 'history' if I use node:child_process?

[Et7f3]

If your intention is to read history then just fs.readFile .bash_history if shell is bash or %userprofile%\AppData\Roaming\Microsoft\Windows\PowerShell\PSReadline\ConsoleHost_history.txt if shell is pwsh. You will get better performance no process loading.