Node.js: console.log message doesn't show up if method throws exception... why?

Question

In Node.js, if I have a method that throws an exception, console.log statements from that method don't fire. I recognize that in the simple test case below that I should catch the exception from the readFileSync call, or otherwise be defensive about it. Just curious if someone could explain the behavior to me.

Simple test case:

var fs = require('fs');

function readAFileThatDoesntExist(filename) {
    console.log(filename);
    fs.readFileSync(filename);
}

console.log("We're about to read a file that doesn't exist!");
readAFileThatDoesntExist("afile");

Output:

$ node test.js
We're about to read a file that doesn't exist!

fs.js:338
  return binding.open(pathModule._makeLong(path), stringToFlags(flags), mode);
                 ^
Error: ENOENT, no such file or directory 'C:\blog\projects\bloggen\scripts\afile'
    at Object.fs.openSync (fs.js:338:18)
    at Object.fs.readFileSync (fs.js:182:15)
    at readAFileThatDoesntExist (C:\blog\projects\bloggen\scripts\test.js:5:8)
    at Object.<anonymous> (C:\blog\projects\bloggen\scripts\test.js:9:1)
    at Module._compile (module.js:449:26)
    at Object.Module._extensions..js (module.js:467:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Module.runMain (module.js:492:10)
    at process.startup.processNextTick.process._tickCallback (node.js:244:9)

It works as expected for me (Node 0.10.10)

JJJ
– JJJ

2013-11-01 18:58:50 +00:00
Commented Nov 1, 2013 at 18:58 — JJJ
– JJJ, Commented Nov 1, 2013 at 18:58
Works for me as well (v0.10.21).

matth
– matth

2013-11-01 19:00:43 +00:00
Commented Nov 1, 2013 at 19:00 — matth
– matth, Commented Nov 1, 2013 at 19:00
Yeah, didn't realize how far back my node was... thanks.

Shaun
– Shaun

2013-11-01 19:01:48 +00:00
Commented Nov 1, 2013 at 19:01 — Shaun
– Shaun, Commented Nov 1, 2013 at 19:01

Community · Accepted Answer · 2017-05-23 12:10:12Z

26

Ah, figured it out.

It seems that console.log isn't finishing before the process exits... If I use console.warn, the message does show up.

This post explains it: is node.js' console.log asynchronous?

Also, I'm on an older version (0.8.15), so this may no longer be relevant.

edited May 23, 2017 at 12:10

CommunityBot

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answered Nov 1, 2013 at 19:00

Shaun

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2 Comments

klewis Over a year ago

Many many thanks on sharing the alternative option of console.warn when working with node.js

worldsayshi Over a year ago

Somehow this is relevant on node v18.12.1.

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