How can I read a file from a C++ file launched in a Python subprocess?

Question

I'm trying to launch a C++ file using the python function "subprocess". I can begin the execution of the program, but it does not manage to read the data file I put in parameter.

However, when I lauch the C++ file directly with the same path to the same data the program works perfectly.

Do you have any ideas on why it does not work using a subprocess ?

The command line I'm using in my python file looks like this:

datafilePath="/home/*...*/dataFile.txt"

subprocess.run(["./programName", "-f "+datafilePath, (OtherOptionsWorkingFine) ],  cwd="./pathToMyProgram")

"does not manage" is not a description of the problem. What does it say? Did you try debugging the program? — Quimby
– Quimby, Commented Oct 25, 2021 at 9:06
If you print out the argv argument array in your C++ program - one value per line so you can distinguish whitespace within and between arguments - you'll see the difference immediately. — Useless
– Useless, Commented Oct 25, 2021 at 9:43

shoaloak · Accepted Answer · 2021-10-25 09:23:23Z

4

I think you are adding the datafilePath argument wrongly. Try to add all args as separate list items instead of concatenating (some of) them together as a string.

e.g.

subprocess.run(["./programName", "-f", datafilePath, (OtherOptionsWorkingFine) ],  cwd="./pathToMyProgram")

answered Oct 25, 2021 at 9:23

shoaloak

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1 Comment

Charc Over a year ago

Thank that was the problem ! At first it did not work, but that was because I added a space where it was not needed ( I used "-f " instead of "-f")

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