print() statements in Flutter are truncated in flutter run output

[DanTup]

Originally raised at Dart-Code/Dart-Code#1223 by @rajeshzmoke. If you print() a long string in Flutter, it gets truncated with <…> in the flutter run output:

void main() {
  print('a' * 100 + 'b' * 100 + 'c' * 100 + 'd' * 100 + 'e' * 100 + 'f' * 100 +
      'g' * 100 + 'h' * 100 + 'i' * 100 + 'j' * 100 + 'k' * 100);
  runApp(const GalleryApp());
}

I'm using the iOS Simulator - it's possible this is a limitation of how we're reading the logs from the device, I'm not sure.

[iozozturk]

This took my hours to debug, because I was relying on logs and copying access token from there. I was using new experimental log window in Android Studio flutter plugin. No <..> truncation indication there sadly, so didn't realize truncation going on.

[trevorwang]

@iozozturk

I have met the same issue. I was trying to print access_token from oauth, but it's trunked. The iPhone X simulator was being used.

eyJ0eXAiOiJKV1QiLCJub25jZSI6IkFRQUJBQUFBQUFDNXVuYTBFVUZnVElGOEVsYXh0V2pUNk85Wmd4ZkE5dEo0MjdvWkdmc3hWUkJhMXNnNlNGOGwtVktMTGlxVHRYQTVGX0VpQWdBZkwzRzlybFl0c05IQTBiSUR1ZERESk43bVlNU284cHU0TFNBQSIsImFsZyI6IlJTMjU2IiwieDV0IjoibmJDd1cxMXczWGtCLXhVYVh3S1JTTGpNSEdRIiwia2lkIjoibmJDd1cxMXczWGtCLXhVYVh3S1JTTGpNSEdRIn0.eyJhdWQiOiJodHRwczovL2dyYXBoLm1pY3Jvc29mdC5jb20vIiwiaXNzIjoiaHR0cHM6Ly9zdHMud2luZG93cy5uZXQvNzU3YzdmNGItNjQyNy00M2Y4LWI3Y2EtZTQ5NmQ1OTVjZjJhLyIsImlhdCI6MTU0NTM1NjcwOSwibmJmIjoxNTQ1MzU2NzA5LCJleHAiOjE1NDUzNjA2MDksImFjY3QiOjAsImFjciI6IjEiLCJhaW8iOiI0MlJnWUhDZDA5c3RrYUN4ZGZmN2xld2JBNlBxRkpzSzN4M1paN2ZzbkJESDhjWW5KajhCIiwiYW1yIjpbInB3ZCJdLCJhcHBfZGlzcGxheW5hbWUiOiJBcHBDZW50ZXIiLCJhcHBpZCI6IjIxOGZlZmYyLWI5ZWItNGUxYi04Y2U5LTc0NzcyZGZhYzQwYiIsImFwcGlkYWNyIjoiMCIsImZhbWlseV9uYW1lIjoiVHJldm9yIiwiZ2l2ZW5fbmFtZSI6IldhbmciLCJpcGFkZHIiOiIyMDIuNjQuNTMuOTAiLCJuYW1lIjoiVHJldm9yIFdhbmciLCJvaWQiOiI5ZmMwMWE5MS05YzQyLTQ2OTEtOTNlMy1mMDNhZTc1MTE5NTMiLCJwbGF0ZiI6IjIiLCJwdWlkIjoiMTAwM0JGRkRBQkZCNzhGQiIsInNj<…>

[✓] Flutter (Channel stable, v1.0.0, on Mac OS X 10.13.6 17G4015, locale en-CN)
    • Flutter version 1.0.0 at /Users/xxxx/Dev/flutter/contribution/flutter
    • Framework revision 5391447fae (3 weeks ago), 2018-11-29 19:41:26 -0800
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    • Platform android-28, build-tools 28.0.3
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[✓] Android Studio (version 3.2)
    • Android Studio at /Applications/Android Studio.app/Contents
    ✗ Flutter plugin not installed; this adds Flutter specific functionality.
    ✗ Dart plugin not installed; this adds Dart specific functionality.
    • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1136-b06)

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[✓] Connected device (2 available)
    • Android SDK built for x86 • emulator-5554                        • android-x86 • Android 4.4.2 (API 19) (emulator)
    • iPhone X                  • B7435AC0-56E2-4DCC-88C9-85E97326097E • ios         • iOS 12.1 (simulator)

[SachinGanesh]

You can use debugPrint instead of print to log long text
https://flutter.io/debugging/#print-and-debugprint-with-flutter-logs
https://stackoverflow.com/a/49156942/8059845

[trevorwang]

@SachinGanesh I used debugPrint also, but it doesn't work.

[aaronfg]

Having this exact issue. I've resorted to a janky overlayed TextField that I can toggle on that mirrors the log output and is text-selectable.

Really annoying.

[andrewackerman]

Can confirm that both print and debugPrint truncate console output when testing on an iOS device.

[Suraj-Tiwari]

@trevorwang
This could be the dirtiest workaround in the history of mankind but it works.
what i did is first
print(auth.idToken.toString());
in this way you'll get truncated string. copy it and write somewhere.

then replace first statement with this
print(auth.idToken.replaceAll(previousTruncatedString, "")toString());
with this you'll get rest of the string

[trevorwang]

@Suraj-Tiwari Thanks. will have a try.

[DanTup]

This could be the dirtiest workaround in the history of mankind but it works.

A slightly nicer workaround might be to create your own print that splits into smaller chunks, then you don't need to modify the code for each long string. Eg.:

void printWrapped(String text) {
  final pattern = new RegExp('.{1,800}'); // 800 is the size of each chunk
  pattern.allMatches(text).forEach((match) => print(match.group(0)));
}

(note: I haven't battle-tested that function but it worked in a quick test..).

[ghost]

I had a very long json string to be printed out but in the console i saw a single string truncated so i used this method (if can be helpful for someone):

JsonEncoder encoder = new JsonEncoder.withIndent('  ');
String prettyprint = encoder.convert(yourJsonString);
debugPrint(prettyprint);

But it works only with json strings, i have not idea about how to do with "normal" strings.
The first thing i think is to add manually a \n after every n characters , for now, while waiting for a stable fix!

[namiwang]

Confirmed here.

I printed and copied a JWT from the console and wasted a few hours in debugging.

At least a trailing ellipsis "…" would be nice.

[markathomas]

Same issue here. I have noticed a 1024 character limit in the console.

[ngprnk]

any fixes for this issue yet ?

[Suraj-Tiwari]

workarounds but no proper fix.

[ineelp]

I checked with full access token length and after printing it. There is a huge difference in size.

[chenenyu]

plz fix this issue.

[andrewackerman]

So as it turns out, this isn't a bug in Flutter. It seems like this is a hard limitation set by the mobile platforms themselves. For iOS, there doesn't seem to be any kind of configuration for it but it does have a (very) dirty fix:

https://stackoverflow.com/questions/39584707/nslog-on-devices-in-ios-10-xcode-8-seems-to-truncate-why

For Android, there doesn't seem to be any fix. Only the workaround of the kind like DanTup mentioned:

https://stackoverflow.com/questions/8888654/android-set-max-length-of-logcat-messages

[jesobremonte]

There is a second optional parameter in debugPrint you can use to wrap the log text:

debugPrint(someSuperLongString, wrapWidth: 1024);

[Akshar-Patel]

This could be the dirtiest workaround in the history of mankind but it works.

A slightly nicer workaround might be to create your own print that splits into smaller chunks, then you don't need to modify the code for each long string. Eg.:

void printWrapped(String text) {
  final pattern = new RegExp('.{1,800}'); // 800 is the size of each chunk
  pattern.allMatches(text).forEach((match) => print(match.group(0)));
}

(note: I haven't battle-tested that function but it worked in a quick test..).

This is the only workaround that can work easily right now. Thanks @DanTup

[lionnner]

when to fix it? so long time...

[Furtim]

There is a second optional parameter in debugPrint you can use to wrap the log text:

debugPrint(someSuperLongString, wrapWidth: 1024);

This works perfectly. I set it to 1000 rather than 1024 to give some headroom as I wasn't clear whether the 'flutter:' prefix counted in the total, but it splits the message into multiple lines and everything is shown.

Spot on!

[andrewackerman]

Can this issue be locked? It's become an endless cycle of people either requesting an update or posting the same fix/workaround.

[MuhammadAliKhan1]

Any updates on print()? Having the same problem.