node --help | head -n1 throws an error #51448

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1. kvakil commented on Jan 14, 2024

   

   kvakil

   on Jan 14, 2024

   Last edited by kvakil

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   $? after a pipe is the exit code of the last command in the pipe, which in this case is head -n1. That's why you get 0. If you're using Bash, ${PIPESTATUS[0]} will give you the exit code of node --help which in this case is indeed 1.

   expected behaviour is what deno and bun do: don't error lol

   Could you elaborate a little on why you need this? Is it causing issues for you or just something you noticed out of curiosity?
2. jcbhmr

   changed the title [-]`node --help | head -n1` throws an error but still exits with code 0[/-] [+]`node --help | head -n1` throws an error[/+] on Jan 14, 2024
3. jcbhmr commented on Jan 14, 2024

   

   jcbhmr

   on Jan 14, 2024

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   Ohhhh so that's why it exited with code 0! 🤦‍♀️

   Context of how I noticed this: I was trying to trim the massive --help menus of a bunch of different commands like clang, deno, bun, cargo, rustc, node, etc. and node --help | head -n20 failed. 🤷‍♀️
4. jcbhmr commented on Jan 14, 2024

   

   jcbhmr

   on Jan 14, 2024

   Last edited by jcbhmr

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   This works:

   node -e 'console.log("a\n".repeat(2000))' | head -n5

   This works:

   node -e 'process.stdout.write("a\n".repeat(2000))' | head -n5

   This is what the node --help printing code looks like:

   node/lib/internal/main/print_help.js

   Lines 200 to 233 in c25878d

   	function print(stream) {
   	const { options, aliases } = require('internal/options');
   	// Use 75 % of the available width, and at least 70 characters.
   	const width = MathMax(70, (stream.columns || 0) * 0.75);
   	const firstColumn = MathFloor(width * 0.4);
   	const secondColumn = MathFloor(width * 0.57);
   	options.set('-', { helpText: 'script read from stdin ' +
   	'(default if no file name is provided, ' +
   	'interactive mode if a tty)' });
   	options.set('--', { helpText: 'indicate the end of node options' });
   	stream.write(
   	'Usage: node [options] [ script.js ] [arguments]\n' +
   	' node inspect [options] [ script.js | host:port ] [arguments]\n\n' +
   	'Options:\n');
   	stream.write(indent(format({
   	options, aliases, firstColumn, secondColumn,
   	}), 2));
   	stream.write('\nEnvironment variables:\n');
   	stream.write(format({
   	options: envVars, firstColumn, secondColumn,
   	}));
   	stream.write('\nDocumentation can be found at https://nodejs.org/\n');
   	}
   	prepareMainThreadExecution();
   	markBootstrapComplete();
   	print(process.stdout);

   Specifically note the use of multiple .write() calls.

   This FAILS:

   node -e 'for (const i of Array(1000).keys()) process.stdout.write(`${i}\n`)' | head -n5

   This works:

   node -e 'for (const i of Array(1000).keys()) console.log(i)' | head -n5

   What I suggest:

   • use console.log() which appears to already have this swallowing error behaviour
   • OR if that can't happen: change the node --help printing code to use helpText += partN and .write(helpText) with a try block with a catch (error) and if (error?.code !== 'EPIPE') throw error rethrow

   This would:

   1. Not interfere with the useful and expected feature of throwing on closed pipes
   2. Stop the weird error from happening with node --help
5. aduh95

   closed this as completedin #51463on May 12, 2024
6. aduh95

   added a commit that references this issue on May 12, 2024

   bootstrap: print `--help` message using `console.log`

   ...

   c7d53f0
7. targos

   added a commit that references this issue on May 13, 2024

   bootstrap: print `--help` message using `console.log`

   ...

   5db4c54
8. eliphazbouye

   added a commit that references this issue on Jun 20, 2024

   bootstrap: print `--help` message using `console.log`

   ...

   b78d767