Why can't QFile read from the "~" directory?

Question

I've tried the following short example to find out about a bug in a bigger program I am working on. It looks like QFile doesn't support unix (or the shell's) notation for the home directory:

#include <QFile>
#include <QDebug>

int main()
{
        QFile f("~/.vimrc");
        if (f.open(QIODevice::ReadOnly))
        {
                qDebug() << f.readAll();
                f.close();
        }
        else
        {
                qDebug() << f.error();
        }
}

As soon as I replace the "~" with my real home directory path, it works. Is there an easy workaround - some setting to enable? Or do I have to go the "ugly" way and ask QDir for the home directory of the current user and prepend that manually to each path?

Addendum: It's clear that usually the shell performs the tilde expansion so programs would never see that. Still it is so convenient in unix shells that I hoped the Qt implementation for file access would have that expansion included.

Answer 1

It has nothing to do with not supporting UNIX; the expansion of tildes to the user's home directory is a substitution performed by the shell, so yes, you will have to manually replace them.

Answer 2

Take a look at the C library function glob, which will do tilde expansion (and possibly wildcard expansion and various other functions too).

Answer 3

Why not just create a helper function, something like (untested):

QString morphFile (QString s) {
    if (s.startsWith ("~/"))
        s.replace (0, 1, QDir::homePath());
    return s;
}
:
QFile f(morphFile ("~/.vimrc"));

A more complete solution may be (again untested since I don't have Qt locally, but a competent coder should be able to get this going):

QString morphFile (QString fspec) {
    // Leave strings not starting with tilde.

    if (!fspec.startsWith ("~"))
        return fspec;

    // Special case for current user.

    if (fspec.startsWith ("~/")) {
        fspec.replace (0, 1, QDir::homePath());
        return fspec;
    }

    // General case for any user. Get user name and length of it.

    QString name (fspec);
    name.replace (0, 1, "");
    int len = name.indexOf ('/');
    if (len == -1)
        len = name.length()
    else
        len--;
    name = name.left (idx);

    // Find that user in the passwd file, replace with home directory
    //   if found, then return it.

    struct passwd *pwent = getpwnam (name.toAscii().constData());
    if (pwent != NULL)
        fspec.replace (0, len+1, pwent->pw_dir);

    return fspec;
}

Answer 4

Please submit a suggestion to the Qt bugtracker.

http://bugreports.qt.nokia.com/