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.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<…>

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[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!

[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.

[badelectron77]

I'm heading the same issue in Android Studio. Finally wrote a function for logging which splits the string into pieces:

void logLongString(String s) {
    if (s == null || s.length <= 0) return;
    const int n = 1000;
    int startIndex = 0;
    int endIndex = n;
    while (startIndex < s.length) {
      if (endIndex > s.length) endIndex = s.length;
      print(s.substring(startIndex, endIndex));
      startIndex += n;
      endIndex = startIndex + n;
    }
}

[Aqua-Ye]

you can see the full log output in the DevTools https://flutter.dev/docs/testing/debugging

[zanderso]

Hi folks, please see the solution here: #22665 (comment)