Why does my subprocess.call work only when shell = True? Python

Question

I am using subprocess.call() to execute commands from a specific directory.

Without using shell = True

scrcpyPath = "C:\\Users\\H\\Downloads\\scrcpy-win64-v1.14"
subprocess.call(["scrcpy", "--window-title", "'Mydevice'"], cwd = scrcpyPath)

I get the following error

FileNotFoundError: [WinError 2] The system cannot find the file specified.

I have managed to make it work using `shell = True'

subprocess.call(f"scrcpy --window-title 'Mydevice'", cwd = scrcpyPath, shell = True)

but it stops working when I add whitespace in the window title Mydevice.

subprocess.call(f"scrcpy --window-title 'My device'", cwd = scrcpyPath, shell = True)

I get the following error

ERROR: Unexpected additional argument: 1'

The reason I am using a formatted string is that I want the window title to be a variable, but again - it does not work when I add whitespace.

subprocess.call(f"scrcpy --window-title 'Device {deviceName}'", cwd = scrcpyPath, shell = True)

I found the solution. I think I was wrongly using cwd.

subprocess.call([f"{scrcpyPath}\\scrcpy", "--window-title", f"'{deviceName}'"])

With shell = True, python uses the shell to find where the binary file for the command scrcpy is located. If you don't use that, you need to tell python about the location of that binary yourself. — rdas
– rdas, Commented Jul 2, 2020 at 11:45
@rdas I am not sure what that means, but I will look it up. I thought the location is given by cwd. — user572780
– user572780, Commented Jul 2, 2020 at 11:57

ShadowRanger · Accepted Answer · 2020-07-02 11:51:05Z

3

You didn't split your arguments properly; basically any space-separation in the command-line should be separate arguments, and no shell quoting is needed when they're passed as separate arguments. What you wanted was:

subprocess.call(["scrcpy", "--window-title", "Mydevice"], cwd=scrcpyPath)

answered Jul 2, 2020 at 11:51

ShadowRanger

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user572780 Over a year ago

I have tried that and I have tried subprocess.call(["scrcpy"], cwd = scrcpyPath). It still does not work without shell = True. I get this error: FileNotFoundError: [WinError 2] The system cannot find the file specified

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