Writing a Frontend

[solarwind]

Hey all, I'm using QtCreator (IDE) to write a frontend for a command line app using C++ and Qt 4.

I need to be able to execute the command line app with certain flags, read the output (the program prints progress information as it does its job) and update the GUI (such as progress bars) as the command line app prints out progress information.

How do I do this. I already have a basic GUI going but so far it just uses the system() function to call the command line app. This is annoying because I can't read the output, I have to wait for the process to finish and it lags the output. Because of this, I wont be able to update the GUI.

Can anyone help me?

[cabalas]

What command line app are you trying to write a front end for? just asking as if it is like curl where all of the functionality is separated into a library perhaps the best idea would be to use the library rather than the system function.

[solarwind]

What command line app are you trying to write a front end for? just asking as if it is like curl where all of the functionality is separated into a library perhaps the best idea would be to use the library rather than the system function.

pk2cmd (a microcontroller programmer cmdline interface). There's no library, it's just an app.

[NathanB]

I believe this is what you are looking for:

http://www.gnu.org/software/libtool/manual/libc/Pipe-to-a-Subprocess.html#Pipe-to-a-Subprocess

[samjh]

http://doc.trolltech.com/4.5/qprocess.html

Take a look at the execute and reallAllStandardOutput methods.

[solarwind]

I believe this is what you are looking for:

http://www.gnu.org/software/libtool/manual/libc/Pipe-to-a-Subprocess.html#Pipe-to-a-Subprocess

Thank you.


http://doc.trolltech.com/4.5/qprocess.html

Take a look at the execute and reallAllStandardOutput methods.

Thanks! This is what I was looking for. Also, I need a way to update a progress bar from within a function and I don't know how to do it.

For example, when the user clicks the "Burn!" button, the GUI will call the cmdline program to perform a function. The cmdline program constantly prints the percentage complete (on every new line). I need a way to keep looping and constantly read the percent complete and update a progress bar.

There are two problems:
1. I think the GUI wont refresh until the end of the callback function so even if I keep updating the progress bar, it will only show the final result which is 100%, it wont update in the middle.
2. how do I get the stdout of the cmdline program when it has not yet completed execution? Is it possible with the QProcess class?

[samjh]

how do I get the stdout of the cmdline program when it has not yet completed execution? Is it possible with the QProcess class?

I think readyReadStandardOutput() signal is emitted from QProcess when a line (ie. ending with '\n') is written to stdout. Then you can call readAllStandardOutput() and parse the last line written.

Frankly, I'm not a 100% sure. Google is your friend. :)