QProcess: start a compiled c program and output to textBrowser in Linux

? Offline

Hi, welcome to the forum. Check the ProcessError to get a hint on what went wrong. Also, add a call to waitForStarted and see if it hangs. Judging by the pathname, your a.out is owned by the user root. I assume you're not logged in as root so you probably don't have the sufficient access rights to run that executable.

mrjj

Hi
Besides what @Wieland suggests
did you try open a shell and just type
/root/Desktop/a.out

and see if it can run ?

in some cases it wants
chmod +x a.out

to even be allowed to run.
(normally the compiler / linker does that for you)

JonB

@Naim , @mrjj
If you like trivia (you probably don't...), you can actually execute it without the execute bit set via the accepted answer to https://superuser.com/questions/341439/can-i-execute-a-linux-binary-without-the-execute-permission-bit-being-set :)

mrjj

@JNBarchan
But does it set the bit ?
chmod a-x /tmp/ls

Naim

@Wieland Yes I'm using root. As for ProcessError and waitForStarted I'll reply that later
@mrjj I compiled a.out as the root user

mrjj

@Naim
Ok, so you are logged in as root. so its not just rights issue.
Hopefully ProcessError tells you why it cant run :)

aha_1980

@Naim: As @mrjj already asked earlier before:

Can you run /root/Desktop/a.out from the shell? It might be, that /root is on a partition that is mounted as no-executable. Why has to program to reside below /root?

aha_1980

@mrjj said in QProcess: start a compiled c program and output to textBrowser in Linux:

@JNBarchan
But does it set the bit ?
chmod a-x /tmp/ls

chmod a-x /tmp/ls clears the executable bit ;)

mrjj

@aha_1980
ahh of course its -x :)
my brain said a TO x (facepalm)
So it can run without it using LD and some magic. Cool.

Naim

@aha_1980 Yes I can run it in shell with ./root/Desktop/a.out. I'm using the root user on a virtual machine.

Naim

I may have find the problem here. My C program a.out runs indefinitely and textBrowser only shows the output once my program have finished executing. I've tried to run another C program that accepts command line input to loop how many times. Its output shows up in textBrowser after it has done looping.

jsulm

@Naim Use http://doc.qt.io/qt-5/qprocess.html#readyReadStandardOutput and http://doc.qt.io/qt-5/qprocess.html#readyReadStandardError to get notifications each time the process writes something to stdout or stderr and read it using http://doc.qt.io/qt-5/qprocess.html#readAllStandardOutput and http://doc.qt.io/qt-5/qprocess.html#readAllStandardError. Do not call waitForFinished, just make sure your proc does not go out of scope (make it class member).