Unwanted and annoying backslash in string read from file!

Mohammadsm

I want to read a unicode string from a file. file content is this:
\u0048\u0065\u006c\u006c\u006f

For reasons in my program, I have to use system calls to read the file. So I've done it through QProcess:

execute->start("cat /home/user/x");
execute->waitForFinished(1000);
qDebug()<<execute->readAllStandardOutput();

And the output is: "\\u0048\\u0065\\u006c\\u006c\\u006f". And it can't be decoded to "Hello" .
But when I enter it manually, it's fine!

qDebug()<<"\u0048\u0065\u006c\u006c\u006f";

The output is: "Hello".

How should I overcome this problem?

Thanks in advance

JonB

@Mohammadsm said in Unwanted and annoying backslash in string read from file!:

For reasons in my program, I have to use system calls to read the file. So I've done it through QProcess:

FWIW this makes no sense at all. Running a cat process and reading all standard output in order to read a file is just a crazy inefficient equivalent of using QFile to read its content. I cannot imagine any circumstance where you would need to do this.... But I'll leave it at that.

I want to read a unicode string from a file. file content is this:
\u0048\u0065\u006c\u006c\u006f

How did you get see that string? Do you mean the file length is 5 bytes or do you mean it actually has the string you show (~30 bytes) in it?

Next possibility:

qDebug()<<execute->readAllStandardOutput();

readAllStandardOutput() returns a QByteArray for qDebug() to output.

qDebug()<<"\u0048\u0065\u006c\u006c\u006f";

That is a string/char[]/QString for qDebug() to print.

qDebug() may well display a QByteArray as an array of bytes but a string as a string, hence only the second one will be shown as a string "Hello". Don't rely on qDebug() as an informative way to display content, it's intended to be human-readable only.

Mohammadsm

Thank you @JonB

Do you mean the file length is 5 bytes or do you mean it actually has the string you show (~30 bytes) in it?

It's 30 bytes, just like it is.

\\u0048\\u0065\\u006c\\u006c\\u006f

I just want to know why there is an extra backslash in QProcess::readAllStandardOutput()?

Don't rely on qDebug() as an informative way to display content, it's intended to be human-readable only.

I tried with QTextCodec::fromUnicode(const QString &str) but it failed due to this additional backslash.

jsulm

@Mohammadsm said in Unwanted and annoying backslash in string read from file!:

I just want to know why there is an extra backslash in QProcess::readAllStandardOutput()?

I guess because you used qDebug to print it...

JonB

@Mohammadsm said in Unwanted and annoying backslash in string read from file!:

It's 30 bytes, just like it is.

Then is not a Unicode string. And your "when I enter it manually as qDebug()<<"\u0048\u0065\u006c\u006c\u006f";" is totally different. Rather the file content is a "human visual representation of the 5 Unicode characters forming the C++ literal string". I do not know of any C++ or Qt function which would convert between the two, you would have to write one yourself. And just to complicate things further, your original was \u0048\u0065\u006c\u006c\u006f, which is 30 bytes, but now you say the file contains \\u0048\\u0065\\u006c\\u006c\\u006f which is 35 bytes and different again....

I just want to know why there is an extra backslash in QProcess::readAllStandardOutput()?

readStandardOutput() does not return/put in any "extra backslashes" (or any other character). I already informed you about the output format of qDebug(), which does not show precisely, one-for-one what characters you are looking at.

I tried with QTextCodec::fromUnicode(const QString &str) but it failed due to this additional backslash.

First you have two posts claiming two different contents for the file, backslash-wise. Second if you really want to get rid of every backslash, or reduce double-backslashes to single-backslash, use something like replace(). And thirdly as I said above if your file does indeed contain either 30 or 35 bytes it is not a "Unicode string" (like your C++ string is) and QTextCodec::fromUnicode() is not going to work on it or produce what you think.

Mohammadsm

@jsulm
I tried QChar to convert unicode and my problem solved. now qDebug prints the text correctly. 👌🏻
I also copied the readAllStandardOutput() to a QString and removed backslashes via remove("\x5C\x75").