Node-cli freeze after Spawning a child_process - node.js

Question

The cli could not receive keyboard input after execution, and this also includes 'ctrl-c' and 'ctrl-z', thus you have to manually exit the program. It gave me a lot of trouble, please take a look at it;
var { exec, spawn } = require("child_process");
let cmd = (cmdline, consolelog = true) => {
return new Promise((resolve, reject) => {
let cmdarray = cmdline.split(" ");
let result = "";
let error = "";
let child = spawn(cmdarray.shift(), cmdarray);
process.stdin.pipe(child.stdin);
child.stdout.setEncoding("utf8");
child.stderr.setEncoding("utf8");
child.stderr.on("data", data => {
if (consolelog) process.stdout.write(data.toString());
error = data.toString();
});
child.stdout.on("data", data => {
if (consolelog) process.stdout.write(data.toString());
result = data.toString();
});
child.on("close", code => {
if (consolelog) process.stdout.write(`Exit code: ${code}\n`);
code == 0 ? resolve(result) : reject(error);
});
});
};
OS: osx & ubuntu 19.04
Test case:
cmd("echo hi");
Edit:
Normal circumstances : put the code inside myprogram.js and use node myprogram.js to activate the script. It works perfectly, and you can also try different commands. HOWEVER, if you put following code by using
$ node
> let cmd = require(PATH_TO_CMD_FUNCTION)
> cmd("echo hi");
The node-cli will freeze and stop listening to your keyboard input.
Edit 2:
Found out, you need to channel through {stdio: "inherit"}

Answer 1

UPDATED ANSWER:
I trimmed down your spawner a little in order to be succinct, and eliminate any other possibilities. There is one common test case I could find to reproduce stated issue regarding signals, keyboard shortcuts, and trapped input.
If you spawn the 'sh' command, you will not be able to escape from the spawned process by means of conventional signal keyboard shortcuts. This is because node.js "traps" the input and forwards it directly to the spawned process.
Most processes allow killing via signalling through keyboard shortcuts such as CTRL-C. 'sh', however, does not-- and so is a perfect example.
The only ways to exit are to use the 'exit' command, close the window (which may possibly leave the spawned process running in the background), reboot your machine, etc. Also, internally or by other means sending a signal, but not via stdin or equivalent.
Your CTRL-C input, in other words, is "normally working" not because it is killing your node app, but because it is being forwarded to the spawned process and killing it.
The spawned process will continue to trap your input if it is immune.
require("child_process").spawn("sh", {
shell: true,
encoding: 'utf8',
stdio: [0,1,2]
});
This may not be the best example for your specific program, but it illustrates the principle, which is the closest I can come since I cannot replicate with the given test case (I have tried it on my phone, my laptop, and my cloud server, three different versions of node, two different versions of Ubuntu).
In any case, it sounds like your stdin is not being "let go" by the spawned process. You may need to "reassign" it to the original process.stdin .
As stated here:
https://node.readthedocs.io/en/latest/api/child_process/
Also, note that node establishes signal handlers for 'SIGINT' and
'SIGTERM', so it will not terminate due to receipt of those signals,
it will exit.
PREVIOUSLY:
It looks like your cmd function is only getting one argument (the command itself) due to the split and shift. Spawn expects a string with the whole command, so likely it is only getting "echo" without "hi", so it isn't exiting due to hanging on "echo". May need to append a newline ("\n") as well.
It also may help to nest the command in an sh command that then executes it, so it runs in a shell.
Like this:
var { exec, spawn } = require("child_process");
let cmd = (cmdline, consolelog = true) => {
return new Promise((resolve, reject) => {
let result = "";
let error = "";
// This. Note the shell option.
let child = spawn(cmdline, {shell:true});
process.stdin.pipe(child.stdin);
child.stdout.setEncoding("utf8");
child.stderr.setEncoding("utf8");
child.stderr.on("data", data => {
if (consolelog) process.stdout.write(data.toString());
error = data.toString();
});
child.stdout.on("data", data => {
if (consolelog) process.stdout.write(data.toString());
result = data.toString();
});
child.on("close", code => {
if (consolelog) process.stdout.write(`Exit code: ${code}\n`);
code == 0 ? resolve(result) : reject(error);
});
});
};
cmd("echo hello");
Output:
hello
Exit code: 0