Checking Bash Exit Code Launch a terminal, and run any command. Check the value of the shell variable “$?” for the exit code. $ echo $? As the “date” command ran successfully, the exit code is 0.
Extracting the elusive exit code To display the exit code for the last command you ran on the command line, use the following command: $ echo $?
Method 1: Using ctrl+C key: When running a program of NodeJS in the console, you can close it with ctrl+C directly from the console with changing the code shown below: Method 2: Using process. exit() Function: This function tells Node. js to end the process which is running at the same time with an exit code.
Those 2 commands are running in separate shells.
To get the code, you should be able to check err.code
in your callback.
If that doesn't work, you need to add an exit
event handler
e.g.
dir = exec("ls -la", function(err, stdout, stderr) {
if (err) {
// should have err.code here?
}
console.log(stdout);
});
dir.on('exit', function (code) {
// exit code is code
});
From the docs:
If a
callback
function is provided, it is called with the arguments(error, stdout, stderr)
. On success,error
will benull
. On error,error
will be an instance of Error. Theerror.code
property will be the exit code of the child process whileerror.signal
will be set to the signal that terminated the process. Any exit code other than 0 is considered to be an error.
So:
exec('...', function(error, stdout, stderr) {
if (error) {
console.log(error.code);
}
});
Should work.
child_process.spawnSync()
This function exposes the nicest sync interface: https://nodejs.org/api/child_process.html#child_process_child_process_spawnsync_command_args_options
Example:
#!/usr/bin/env node
const child_process = require('child_process');
let out;
out = child_process.spawnSync('true');
console.log('status: ' + out.status);
console.log('stdout: ' + out.stdout.toString('utf8'));
console.log('stderr: ' + out.stderr.toString('utf8'));
console.log();
out = child_process.spawnSync('false');
console.log('status: ' + out.status);
console.log('stdout: ' + out.stdout.toString('utf8'));
console.log('stderr: ' + out.stderr.toString('utf8'));
console.log();
out = child_process.spawnSync('echo', ['abc']);
console.log('status: ' + out.status);
console.log('stdout: ' + out.stdout.toString('utf8'));
console.log('stderr: ' + out.stderr.toString('utf8'));
console.log();
Output:
status: 0
stdout:
stderr:
status: 1
stdout:
stderr:
status: 0
stdout: abc
stderr:
Tested in Node.js v10.15.1, Ubuntu 19.10.
In node documentation i found this information for the callback function:
On success, error will be null. On error, error will be an instance of Error. The error.code property will be the exit code of the child process while error.signal will be set to the signal that terminated the process. Any exit code other than 0 is considered to be an error.
If anyone is looking for an await
/Promise
version:
const exec = require('util').promisify(require('child_process').exec);
let out = await exec(`echo hello`).catch(e => e);
console.log(out.stdout); // outputs "hello"
console.log(out.code); // Note: `out.code` is *undefined* if successful (instead of 0).
If the command is successful, then the it'll output an object like {stderr, stdout}
. If it has a non-zero exit code, then it'll output an error object with {stderr, stdout, code, killed, signal, cmd}
and the usual JavaScript Error
object properties like message
and stack
.
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