QProcess starting on macos only when run from terminal

cupboard_

windows has no issues
when ran from terminal ("./test.app/Contents/MacOS/test") also works as expected

but when i try to run it from the application bundle itself (double clicking test.app) QProcess does not start
QProcess::errorString() returns "Child process set up failed: execve: No such file or directory" (checked using a dialog window)

the executable i'm trying to run is in my path and is accessible via the terminal

proc.start("ffmpeg", QStringList() << "-i" << filename << arguments);

SGaist

Hi,

Where is ffmpeg located exactly on your machine ?

cupboard_

/usr/local/bin/ffmpeg

Axel Spoerl

Add this line before you start the process:

qInfo() << __FUNCTION__ << proc.processEnvironment();

… to check the process’ environment.
Looks like /usr/local/bin is in the path of your shell, but not when the app is run from the bundle. See here how to add it.

JonB

@Axel-Spoerl
If you are proposing calling QProcess::setProcessEnvironment() to change the PATH to include /usr/local/bin for the child, I think there is a 50-50 (or greater?) chance this will not affect the parent's ability to find and run the subprocess. I believe --- but not sure --- that the child process environment only affects what environment the child inherits after it has been spawned successfully. Changing PATH in this way won't help the parent find the child to spawn?

I think we found this with QProcess::setWorkingDirectory(): you cannot use it in order to spawn some ./executable living in a directory because it is not set before the executable is spawned, it is only set for the child after it has been located and spawned.

@cupboard_
If it is an issue finding ffmpeg why don't you start by trying proc.start("/usr/local/bin/ffmpeg", ...)? If that resolves, and QProcess::setProcessEnvironment() does not, you may have to change the PATH in the parent before spawning the child if you want it found via PATH.

cupboard_

@JonB

If it is an issue finding ffmpeg why don't you start by trying proc.start("/usr/local/bin/ffmpeg", ...)? If that resolves, and QProcess::setProcessEnvironment() does not, you may have to change the PATH in the parent before spawning the child if you want it found via PATH.

adding /usr/local/bin to the programs path does not help, calling proc.processEnvironment() returns the updated path, but ffmpeg still doesn't run

using proc.start("/usr/local/bin/ffmpeg", QStringList() << "-i" << filename << arguments); does work tho

i tried searching how to change the path in the parent, but i didn't find a way to do it

JonB

@cupboard_ said in QProcess starting on macos only when run from terminal:

i tried searching how to change the path in the parent, but i didn't find a way to do it

You would do that by changing the parent/calling process's environment variable PATH. Nothing to do with QProcess, and you would need to do it before trying to do the QProcess::start() of the child. You can use getenv()/putenv() to read/write the parent process's environment variables (e.g. PATH) if you want to examine or change them.

Kent-Dorfman

ffmpeg also needs access to a bunch of .so libraries. In linux those must be in standard locations or found via the LD_LIBRARY_PATH var. re QProcess::setProcessEnvironment IS the preferred way to make sure the the PATH and LD_LIBRARY_PATH are set properly. Also, QProcess::setWorkingDir is a good idea if the child will reference things by relative path offset.

This is the correct way to do it.

QProcess process;
QProcessEnvironment env = QProcessEnvironment::systemEnvironment();
env.insert("TMPDIR", "C:\\MyApp\\temp"); // Add an environment variable
process.setProcessEnvironment(env);
process.start("myapp");

So no, @Axel-Spoerl ...the environment is set up BEFORE the child is started.

cupboard_

@JonB said in QProcess starting on macos only when run from terminal:

You can use getenv()/putenv() to read/write the parent process's environment variables (e.g. PATH) if you want to examine or change them.

thank you, this worked!

SGaist

One other possible option that might also make your users happy: have a setting in your application that allows to set the path to ffmpeg so if they have a custom version they want to use, they can change for it. You can populate that value checking for known paths.