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file name change to unix file with escaping



  • Hi,

    I developed my app in Mac and when I transfer to the linux there is qfile file read problem due to some of the file and dirs has " " spaces.

    I try to QString.replace(" " , "\" ) and looks replaced .

    but even I saw the file name escaped with \ in linux , it says cant find the name.

    is there any best practices to change file name to readable format in linux ?



  • @RahibeMeryem said in file name change to unix file with escaping:

    I try to QString.replace(" " , "\" ) and looks replaced .

    As it stands copied from your post, this would not even compile. So it's not possible to know what you intended?

    I have never used Mac, but I thought it had a Linux file/pathname syntax, so I don't know what you mean about the problem with spaces. What do you mean about "readable format in linux"?

    Unless someone else knows what this issue is about, you might like to explain just what sort of problem you are having?



  • @JonB

    Mac os path : file = "/Users/xxx/test dene biri/adf.jpg"

    This can be read by Qt QFile (file)

    but in Linux there is space problem.

    I mean that.



  • @RahibeMeryem

    Mac os path : file = "/Users/xxx/test dene biri/adf.jpg"
    

    but in Linux there is space problem.

    No, there isn't. If that path exists on a Linux file system, QFile() will be able to open/read it.

    But if it's not there, it won't. You do have that directory, /Users/xxx/test dene bir, on your Linux box, don't you?

    What exactly is the problem?



  • I'd suggest using perl to rename the files in question, replacing spaces with underscores...and as a I policy I prohibit folks from ever putting spaces in filenames. It's bad practice in any platform.

    #! /usr/bin/perl
    
    $q="\x22";
    
    while (<STDIN>) {
        chomp;
        $o=$_;
        s/[\x00-\x2a]//g;
        s/[\x5b-\x5e]//g;
        s/[\x7b-\x7f]//g;
        s/\x60//g;
        s/\x2f//g;
        ($_ ne $o) && system "mv $q$o$q $q$_$q\n";
    };
    
    

    then ls | remove_spaces.pl



  • @Kent-Dorfman

    • Why would you take a Mac name with spaces in it and replace for Linux? In the sense of the OP says the spaces "work" under MacOs but "don't work" under Linux? It may be a convention that Mac often has directories/files with spaces in their names (I don't know) whereas Linux tends not to, but that's a different matter.

    • as a I policy I prohibit folks from ever putting spaces in filenames. It's bad practice in any platform.

    Sorry, but that's just wrong [EDIT: IMHO] --- we may or may not like it, but Windows uses spaces extensively and it is not "bad practice" under Windows, it's standard practice! If your app chooses to prevent creating files with spaces that's up to you, but you can't call it "bad practice" under Windows :)


  • Lifetime Qt Champion

    @JonB said in file name change to unix file with escaping:

    it's standard practice!

    and it causes many issues, you can find examples in this forum :-)
    That's why I avoid spaces in paths and suggest others to do the same.



  • @jsulm
    Yes it causes issues. The question is whether it is "bad practice" given that there a billions of Windows files around the world with spaces in them. Windows uses both directories & file names with spaces in them extensively, whether you or I like it or not. And I'll say one thing: your app may choose not to create thing with spaces because of the coding problems, but if you don't allow for existing things having spaces in them under Windows because you don't believe in it, that is where the problems will arise!


  • Moderators

    @JonB Hold the horses ;)

    Windows also allows you to have umlaute in the path/name, and that can cause even under windows problems.

    Just because Windows allows it doesn't mean its not bad practice.



  • @J-Hilk
    I admit I don't know about umlauts.

    Under Windows, if you don't want to deal with spaces in path/file names, try accepting the default save file name from a new Word document, or try Ctrl+C, Ctrl+V from File Explorer, or try right-click New>Folder, or try executing anything from standard C:\Program Files\... from the command line, or use the standard Save File dialog to get a name from the user, or a million other cases.

    So you're going to say all of these are bad practice under Windows. I don't think we'll get anywhere, because we must have different definitions of "bad practice".


  • Lifetime Qt Champion

    @JonB said in file name change to unix file with escaping:

    So you're going to say all of these are bad practice under Windows

    Using existing system directories with spaces is not bad practice. But using own directories/file names with spaces (or umlauts) is at least questionable. I try to avoid this.



  • @JonB

    yes there is directory and file as below.

    Linux path : file = "/Users/xxx/test dene biri/adf.jpg"
    
    

    QFile("/Users/xxx/test dene biri/adf.jpg") . gives error under ubuntu 19.

    I will double check tonight



  • @RahibeMeryem
    My Ubuntu 19.04, I have to use Python+PySide2 instead of C++ but no matter:

    (py37) jon@ubuntu-19:~$ mkdir "test space"
    (py37) jon@ubuntu-19:~$ echo hello > "test space/file"
    (py37) jon@ubuntu-19:~$ python3
    Python 3.7.3 | packaged by conda-forge | (default, Jul  1 2019, 21:52:21) 
    [GCC 7.3.0] :: Anaconda, Inc. on linux
    Type "help", "copyright", "credits" or "license" for more information.
    >>> from PySide2.QtCore import QFile
    >>> print(QFile("test space/file").exists())
    True
    >>> print(QFile("test space/file").size())
    6
    >>> print(hex(int(QFile("test space/file").permissions())))
    0x6644
    >>> 
    

  • Lifetime Qt Champion

    @RahibeMeryem said in file name change to unix file with escaping:

    @JonB

    yes there is directory and file as below.

    Linux path : file = "/Users/xxx/test dene biri/adf.jpg"
    
    

    QFile("/Users/xxx/test dene biri/adf.jpg") . gives error under ubuntu 19.

    I will double check tonight

    Hi,

    Maybe because there's no /Users folder on Linux.

    The home folder for users under Linux is /home.



  • @RahibeMeryem said in file name change to unix file with escaping:

    yes there is directory and file as below.
    Linux path : file = "/Users/xxx/test dene biri/adf.jpg"

    QFile("/Users/xxx/test dene biri/adf.jpg") . gives error under ubuntu 19.

    On Linux/Unix systems, if you want to access to an user directory, it is preferable to use '~', for example for user foo: QFile("~foo/test dene biri/adf.jpg")

    I don't know if on macOS this is also working.


  • Lifetime Qt Champion

    @KroMignon that's a shell shortcut so it may or may not work depending on what you are doing.
    Using QStandardPaths would be better.



  • But I have asked and the OP confirmed:

    yes there is directory and file as below.

    Linux path : file = "/Users/xxx/test dene biri/adf.jpg"

    So he must have checked that on his Linux he has a /Users/..., for whatever reason. He says the issue is to do with the spaces.



  • @JonB said in file name change to unix file with escaping:

    for whatever reason

    @RahibeMeryem Did you check if the application has read/excecute rights for each sub-directory?



  • @KroMignon Why are you directing this question to me?



  • @RahibeMeryem
    OK, this is bugging me :) So here is a list of steps which will resolve where we are on this issue.

    If you know how to open a terminal/shell/command-prompt-window on Ubuntu:

    1. Open a terminal/shell/command-prompt-window. (Do not type sudo anything, if you might be tempted to.)
    2. Type ls -b /Users
    3. Then ls -b /Users/xxx, with whatever for the xxx
    4. Then ls -b /Users/xxx/test dene biri
    5. Finallyls -b /Users/xxx/test dene biri/adf.jpg
    6. If you really get as far as here without a "No such file or directory"-type error, type ls -l /Users/xxx/test dene biri/adf.jpg
    7. Copy the output you get as you go along and paste it here.

    If you do not know how to open a terminal:

    1. Open the "File Explorer" from its icon on the desktop
    2. Make it browse to the top-level root directory, named /.
    3. Go downwards into directories/folders for your path, i.e. Users, then whatever for the xxx, then test dene biri.
    4. Show us a screenshot (screenshot program, https://help.ubuntu.com/stable/ubuntu-help/screen-shot-record.html) of where you get to.

    P.S.
    I just noticed there is some confusion of whether the path has test dene bir or test dene biri (the extra i at the end) in some of these posts. I may have introduced that inadvertently. Obviously ensure both Mac & Linux code use whichever spelling is correct for you.



  • @JonB @SGaist

    I found the STUPiD problem or a bug:

    one of my folder path include 'ü' . utf8 character with spaces.

    the 'ü' is different between mac os x and linux . in the linux ls -l look %100 identical but its not.

    so I create same folder name with linux 'ü' its working now.

    suprise.



  • @RahibeMeryem

    in the linux ls -l look %100 identical but its not.

    That is precisely why you will see I suggested you use ls -b in all my examples, which I guess is how you spotted it....


  • Moderators

    @RahibeMeryem said in file name change to unix file with escaping:

    @JonB @SGaist

    I found the STUPiD problem or a bug:

    one of my folder path include 'ü' . utf8 character with spaces.

    the 'ü' is different between mac os x and linux . in the linux ls -l look %100 identical but its not.

    so I create same folder name with linux 'ü' its working now.

    suprise.

    Ah, we went full circle, let me quote:

    @jsulm said in file name change to unix file with escaping:

    @JonB said in file name change to unix file with escaping:

    So you're going to say all of these are bad practice under Windows

    Using existing system directories with spaces is not bad practice. But using own directories/file names with spaces (or umlauts) is at least questionable. I try to avoid this.



  • @J-Hilk
    For all we know he has no choice about directory spelling. E.g. if his user name contains an umlaut he types in, I would guess Linux creates his home directory based on this. Perhaps because this is "bad practice" we'd better tell Linux to change its ways.... Or, perhaps the user should change his real name to accommodate...


  • Moderators

    @JonB said in file name change to unix file with escaping:

    Or, perhaps the user should change his real name to accommodate...

    yep, that's what I did at my old work place,
    ü -> ue



  • @J-Hilk a bit OT but touches the good/bad practice part: in my workplace we have around 20 nationalities using 4 or 5 different alphabets. All the names and surnames in the sysaccounts/paths are transliterated to English exactly to avoid problems like that.



  • This vicious bug is due to the fact that Mac file system uses a special variant of unicode called decomposed form (NFD)
    see https://developer.apple.com/library/archive/qa/qa1235/_index.html

    However, you may need to convert to precomposed Unicode when you interact with other platforms.
    For example, the following are all valid reasons why you might want to convert to precomposed Unicode:
    -If you implement a network protocol which is defined to use precomposed Unicode.
    -When creating a cross-platform file (or volume) whose specification dictates precomposed Unicode.
    -If you incorporate a large body of cross-platform code into your application,
    where that code is expecting precomposed Unicode.

    For the same reason, if you're using C/C++ libraries that deal with file paths, it's advisable to use the following method for converting QString to *char:
    [filePath.toNSString() fileSystemRepresentation];



  • @SGaist

    @SGaist said in file name change to unix file with escaping:

    @KroMignon that's a shell shortcut so it may or may not work depending on what you are doing.
    Using QStandardPaths would be better.

    Yes, tilde is a shell shortcut, so should only ever be used in immediate mode on the command line in shells that recognize it. Use anywhere else can and probably will fail to be interpreted properly.



  • @Kent-Dorfman
    Hence @SGaist's comment that you would hardly ever want to construct a QFile("~...") anything. The only times would be for path-splitting function calls (even then be careful, e.g. Qt will think it's a relative path when in effect it's actually absolute), or to convert directly to string for passing to an OS command. Any other operations like trying to open it will not address the intended file (e.g. https://stackoverflow.com/questions/2816499/why-cant-qfile-read-from-the-directory).


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