2016-06-02 13:47 GMT+02:00 Juan Navarro <oneorj...@gmail.com>: > Hello, > > I'm building a GUI tool under Kubuntu Linux 14.04, which among other things, > creates SquashFS (https://en.wikipedia.org/wiki/SquashFS) images with the > command-line command "mksquashfs". Due to the size of the images, this > process takes a good amount of time, so I'd like to show its progress with a > QProgressBar. > > Problem here is that the default output from this command is not really > intended to be parsed. It uses a dynamic progress bar + a progress > percentage which repaint themselves on the terminal, I guess that using the > technique of printing "\r" (carriage returns) without "\n" (line feeds), so > the progress bar is always drawn on the same row of the console output: > > $ mksquashfs /home /tmp/test.sfs -noappend -processors 1 > Parallel mksquashfs: Using 1 processor > Creating 4.0 filesystem on /tmp/test.sfs, block size 131072. > [======================================/ ] 699/1250 75% > > > However I've found the way of printing the progress bar + percentage value > in a serial way, ie. each iteration gets printed on its own line, with the > following command line: > > $ script --return --flush --quiet \ > --command "mksquashfs /home \ > /tmp/test.sfs -info -progress -noappend \ > -processors 1" > test.txt > > With this, the output shown in "file.txt" is somewhat similar to this: > > file ..., uncompressed size 2755336 bytes > [=========\ ] 481/12359 > 3% > file ..., uncompressed size 726904 bytes > [==========\ ] 528/12359 > 4% > file ..., uncompressed size 577 bytes > [==============\ ] 719/12359 > 5% > > This should be really easy to parse, extract the "x%" from the end of the > line, and send that to the QProgressBar. > > So I've ported this command line to my Qt code. This is the relevant part of > the code: > > class MyClass > { > QProcess p; > > void start() { > p.setProcessChannelMode(QProcess::SeparateChannels); > p.setReadChannel(QProcess::StandardOutput); > connect(&p, SIGNAL(readyReadStandardOutput()), > this, SLOT(onProcessReadyReadStdout())); > > QString c = "script"; > QStringList a; > a << "--return" << "--flush" << "--quiet" > << "--command" > << "mksquashfs /media/data/KSHOW_320/RO/home " > "/tmp/test.sfs -info -progress " > "-noappend -no-recovery -processors 1"; > p.start(c, a, QIODevice::ReadOnly | QIODevice::Unbuffered | > QIODevice::Text); > } > > private slots: > void onProcessReadyReadStdout() { > qDebug() << "New data:" << p.readAllStandardOutput(); > } > } > > > The problem is that given this code, the output doesn't contain the progress > bar... > > With Qt 4.8.4: > New data: " > file ..., uncompressed size 2755336 bytes > " > New data: " > file ..., uncompressed size 726904 bytes > " > New data: " > file ..., uncompressed size 577 bytes > " > > With Qt 5.6.0: > New data: "\nfile ..., uncompressed size 2755336 bytes \n" > New data: "\nfile ..., uncompressed size 726904 bytes \n" > New data: "\nfile ..., uncompressed size 577 bytes \n" > > (Note how in Qt 5.6.0 the same command shows a different output, by > explicitly showing '\n' characters; also the flag "QIODevice::Text" doesn't > make a difference here). > > I'm quite lost here, because at this point I assume that QProcess is doing > the right thing, but I don't understand at what point in the command chain > the output is being generated differently between those two different ways > of running the same command. > > It's probably the way the carriage returns are managed in the QProcess vs. > shell redirection to a file, but I'd like to see if anyone here has some > comment.
Maybe it needs a TTY to output the progress bar? That's out of scope for QProcess, but if you're fine with a dependency on kcoreaddons + kpty, it looks like the latter has a KPtyProcess you could use [1]. Elvis [1] https://api.kde.org/frameworks/kpty/html/classKPtyProcess.html > > Regards, > Juan > > _______________________________________________ > Interest mailing list > Interest@qt-project.org > http://lists.qt-project.org/mailman/listinfo/interest > _______________________________________________ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
