This question already has answers here:
How to send output to stderr?
(5 answers)
Closed 6 years ago.
I'm trying to print a formatted string to stderr in Rust (curious newbie here!), but it looks like an easy convenience macro (such as print!/println! for stdout) isn't provided in the standard library.
In C, one could just do it like this:
fprintf(stderr, "format_string", args ...);
I've successfully printed string literals to stderr with
let stderr = std::io::stderr();
writeln!(&mut stderr, "literal");
The next thing that came into mind was to do a format! first, and then use writeln!, mut that fails to compile with error: expected a literal. On the other hand, stderr.write() expects &[u8], so using String::bytes().collect() doesn't really work either..
What are the correct solutions to this?
See answer of the linked duplicate. Since Rust 1.19, you can use the eprintln! macro.
Related
I am learning how work with files in Lua, and I came across a problem.
I know that:
io.output() allows me to specify the file that I will write output to.
The io.write() function simply gets a number of string arguments and writes them to the current output file.
io.close() then closes the file I am reading or writing on.
I first set io.output() to "myNewFile.txt" then I did io.write("Hello World!").
io.output("myNewFile.txt")
io.write("Hello World!")
This part worked well and myNewFile.txt got Hello World written to it.
Then I wrote io.close() to close the myNewFile.txt.
After that, I wrote io.write("Hello World!"), but I got an error:
C:\\Program Files\\lua\\lua54.exe: ...OneDrive\\Documents\\learning lua\\steve's teacher\\main.lua:9: default output file is closed stack traceback: \[C\]: in function 'io.write' ...OneDrive\\Documents\\learning lua\\steve's teacher\\main.lua:9: in main chunk \[C\]: in ?
I wanted io.write("Hello World!") to write Hello World in the terminal. I know can use print() but print() function adds extra characters like \n and things like that.
So my question is, how do I write Hello World in the terminal using io.write("Hello World!") in this situation?
I tried to search this error up on Google, but there weren't any results. I also tried joining many Discord servers, but I didn't get a proper response. I am a new developer to Lua so this all is really confusing to me.
After io.close() do a io.output(io.stdout) to set it back.
The clean way
local oldout = io.output() -- without argument returns actual output
io.output("file") -- set to a filename
-- do file operations here
-- use io.flush() where it is necessary
io.close() -- close file also do a flush()
io.output(oldout) -- set back to oldout ( normally io.stdout )
-- changing io.output() back should also close() and flush() the "file"
-- But better doublecheck this when using userdata without experience
I am trying to create a util for logging.
I need to know the actual differences between print() vs debugPrint() and log().
Many answers I have seen are outdated or confusing. Also, some upvoted answers are contradict.
I am trying to print error messages in red color. I am using ANSI code to achieve it.
debugPrint("\x1B[31m HelloDebug \x1B[0m");
The above one print in red color.
But when i do the same using log(), its not printing in red color. Its escaping the ANSI code.
One thing I found out was log() has error parameter.
If i pass something as error , it handles red color by default.
Here in the first one using log, red is not coming because ANSI code is ignored. But in debugPrint using it's working fine. In third one it takes error red by default. But extra line is added even for empty string message.
Code:
Output:
Is it possible use ANSI code for making color text using log?
Because I have other ANSI code to make different color text.
I dont want use debugPrint because if I print some thing too frequently , the system ignore the logs.
After digging some time I found out that log function is implemented in c++ in the dart runtime.As the log function is external function in dart sdk.
external void log(
String message, {
DateTime? time,
int? sequenceNumber,
int level = 0,
String name = '',
Zone? zone,
Object? error,
StackTrace? stackTrace,
});
https://github.com/dart-lang/sdk/blob/main/runtime/lib/developer.cc
Also I see some different answers while digging.
The below answer says debugPrint only available inside widget class. Is it still true?
https://stackoverflow.com/a/52241553/9248098
EDIT:
While using debugPrint and when I launch app from Android studio terminal, the ANSI color is working in android but when I run it same in iOS its escaping the characters in same Android Studio terminal.
If ANSI code support is based on terminal support, I couldn't figure out why its having issue in same terminal in iOS.
It is well explained in this page Debugging Flutter apps programmatically
debugPrint() is similar to print() but with a throttles applied to prevents being dropped by Android’s kernel.
If you have linter setup on VSCode or other IDE, you will see this warning whenever you use print in your code. For more information, you can refer to Avoid print calls in production code.
To avoid the lint error, you can use kDebugMode with print or debugPrint instead.
if (kDebugMode) {
print('test print');
}
// OR
debugPrint('test debugPrint');
As for log(), it actually allows you to include more information on the logging output. For example, you can add the runtimeType and the relevant object in the log that can help you in debugging the code.
log(
'test log',
name: runtimeType.toString(),
error: myObj,
);
** btw I tried log with ANSI code log("\x1B[31m HelloDebug \x1B[0m");, it is working as expected.
I don't have a lot of coding experience, did some C a few years ago, so that helps, but Lua handles things a bit differently, so I can't keep track.
I sometimes (not always) get this error when a friend or guildy logs into the game:
Date: 2013-06-14 16:57:57
ID: -1
Error occured in: Global
Count: 4
Message: ..\AddOns\Tukui\scripts\chat.lua line 335:
attempt to concatenate upvalue 'classColor' (a nil value)
Debug:
[C]: ?
Tukui\scripts\chat.lua:335: AddMessage()
..\FrameXML\ChatFrame.lua:2755: ChatFrame_MessageEventHandler()
..\FrameXML\ChatFrame.lua:2491: ChatFrame_OnEvent()
...s\WIM\Libs\LibChatHandler-1.0\LibChatHandler-1.0.lua:281:
...s\WIM\Libs\LibChatHandler-1.0\LibChatHandler-1.0.lua:252
...s\WIM\Libs\LibChatHandler-1.0\LibChatHandler-1.0.lua:308:
...s\WIM\Libs\LibChatHandler-1.0\LibChatHandler-1.0.lua:296
I have to do a reload of the ui after this happens to be able to see chat text again for that person.
Line 335 in that .lua file is this:
text = replace(text, "^|Hplayer:(.+)|h%[(.+)%]|h", "|Hplayer:%1|h|cff"..classColor.."%2|r|h")
Now I've learned that the .. indicates the concatenate function, but that isn't really helping me.
I don't know if this is enough information, but if you need it I can post the whole local function or whatever else is required.
If it makes any difference, I'm running the 3.3.5a WoW client.
You are probably using a global that gets defined from some other addon in a now deterministic way
While the (classColor or "") will get you rid of the error, you should try and find why that variable (classColor) is sometimes defined and sometimes not. Maybe it happens only for certain classes?
A simple hack would be to just replace
..classColor..
with
..(classColor or "")..
where it will select a blank string when classColor has no value assigned to it.
This question already has answers here:
How do you convert an iPhone OSStatus code to something useful?
(19 answers)
Closed 9 years ago.
I can easily find noErr = 0 in the OS X library source code. But it's pretty hard to find a full list of error code for OSStatus on iOS.
On Mac OS X, it's not that hard to find stuff like
kAudioHardwareUnsupportedOperationError
But I can't seem to find useful info for iOS OSStatus codes. It would be nice to have a full list of them or any pointers to the header files that define them.
Thanks!
UPDATE:
I don't think my question is a duplicate of the above question. The op of that "possible duplicate" question wanted to convert the 4-char codes he already knew into human-readable strings. Instead, here is my further spec:
I don't even know what 4-char or typedefed integers to use for iOS.
I'd like to see something like a full list of codes, like you would normally see in many C++ framework/library design, e.g., an enum list, or standard exceptions, or even the OSX k-something codes, which at least can be found in the Xcode docs alone.
My usecases of these codes include:
In my custom functions, e.g., some CoreAudio callbacks that have to return OSStatus, I'd like to return these built-in human-readable codes to indicate the types of runtime errors. Without the list, I don't know what to return, other than noErr.
Apparently, many OSX k-codes are undefined under iOS environment so they can't be used transparently.
UPDATE (CONCLUSION):
I finally found a clue: Search for keyword "Result Codes" in Xcode documentation (Organizer) and we get more or less categorized return codes documentation sections in the "System Guides" result. This is good enough for my original question. –
The best I can do to help is provide the results of using find from the command line:
$ cd /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS6.1.sdk
$ find . -name \*.h -exec fgrep -l OSStatus {} \;
./System/Library/Frameworks/AudioToolbox.framework/Headers/AudioConverter.h
./System/Library/Frameworks/AudioToolbox.framework/Headers/AudioFile.h
./System/Library/Frameworks/AudioToolbox.framework/Headers/AudioFileStream.h
./System/Library/Frameworks/AudioToolbox.framework/Headers/AudioFormat.h
./System/Library/Frameworks/AudioToolbox.framework/Headers/AudioQueue.h
./System/Library/Frameworks/AudioToolbox.framework/Headers/AudioServices.h
./System/Library/Frameworks/AudioToolbox.framework/Headers/AudioSession.h
./System/Library/Frameworks/AudioToolbox.framework/Headers/AudioToolbox.h
./System/Library/Frameworks/AudioToolbox.framework/Headers/AUGraph.h
./System/Library/Frameworks/AudioToolbox.framework/Headers/ExtendedAudioFile.h
./System/Library/Frameworks/AudioToolbox.framework/Headers/MusicPlayer.h
./System/Library/Frameworks/AudioUnit.framework/Headers/AUComponent.h
./System/Library/Frameworks/AudioUnit.framework/Headers/AudioComponent.h
./System/Library/Frameworks/AudioUnit.framework/Headers/AudioOutputUnit.h
./System/Library/Frameworks/AudioUnit.framework/Headers/AudioUnitProperties.h
./System/Library/Frameworks/AudioUnit.framework/Headers/MusicDevice.h
./System/Library/Frameworks/CoreFoundation.framework/Headers/CFBase.h
./System/Library/Frameworks/CoreFoundation.framework/Headers/CFError.h
./System/Library/Frameworks/CoreFoundation.framework/Headers/CFStream.h
./System/Library/Frameworks/CoreMedia.framework/Headers/CMAudioClock.h
./System/Library/Frameworks/CoreMedia.framework/Headers/CMBase.h
./System/Library/Frameworks/CoreMedia.framework/Headers/CMBlockBuffer.h
./System/Library/Frameworks/CoreMedia.framework/Headers/CMBufferQueue.h
./System/Library/Frameworks/CoreMedia.framework/Headers/CMFormatDescription.h
./System/Library/Frameworks/CoreMedia.framework/Headers/CMSampleBuffer.h
./System/Library/Frameworks/CoreMedia.framework/Headers/CMSimpleQueue.h
./System/Library/Frameworks/CoreMedia.framework/Headers/CMSync.h
./System/Library/Frameworks/CoreMIDI.framework/Headers/MIDIDriver.h
./System/Library/Frameworks/CoreMIDI.framework/Headers/MIDIServices.h
./System/Library/Frameworks/CoreMIDI.framework/Headers/MIDISetup.h
./System/Library/Frameworks/CoreMIDI.framework/Headers/MIDIThruConnection.h
./System/Library/Frameworks/Foundation.framework/Headers/NSError.h
./System/Library/Frameworks/MediaToolbox.framework/Headers/MTAudioProcessingTap.h
./System/Library/Frameworks/Security.framework/Headers/SecBase.h
./System/Library/Frameworks/Security.framework/Headers/SecIdentity.h
./System/Library/Frameworks/Security.framework/Headers/SecImportExport.h
./System/Library/Frameworks/Security.framework/Headers/SecItem.h
./System/Library/Frameworks/Security.framework/Headers/SecKey.h
./System/Library/Frameworks/Security.framework/Headers/SecTrust.h
./System/Library/Frameworks/Security.framework/Headers/SecureTransport.h
./usr/include/AssertMacros.h
./usr/include/Endian.h
./usr/include/MacTypes.h
Starting here - Embedding F# interactive - I've been trying to embed FSI in my application.
However, I'm getting weird stuff back from StandardOutput.
for example, in standard FSI, if I send this:
let a = 3;;
I get this back:
[empty line here]
val a : int = 3
[empty line here]
> |
(with Pipe representing the input position)
But if I send let a = 3;; to StandardInput, I get this back on StandardOutput:
>
val a : int = 3
|
Has anyone else tried this? Is there something I'm doing wrong, and if not is there any way to work around this? None of the things I've tried so far work, and before I try the 'worse' thing I can think of (set a timer after sending stuff, add the > myself on timeout), I'd like to know if there is a better way!
When embedding F# Interactive, Visual Studio uses the --fsi-server:<some value> parameter.
As far as I know, this does two things:
Changes the way output is printed (instead of printing >, it prints SERVER-PROMPT> on a separate line, so it should be easier to remove it from the output and detect state when input is expected)
It also starts some .NET Remoting channel that you can use to stop execution of commands in F# Interactive (e.g. if it runs into an infinite loop) and it can also provide some completion information.
The F# Interactive pad in MonoDevelop F# plugin uses the flag (see source code on GitHub). I think it works mostly right, but I believe it sometimes prints additional \n in the output.