We Keep Coding

Why can't I use "subprocess" to execute "chown" to change ownership on a directory of files?

I'm trying to use the following "subprocess" command in Python to attempt to change the user and group of a directory of files:
output = subprocess.run(["sudo", "chown", "-R", "user:group", "{}/data/*".format(workingDirectory)],
encoding="utf-8",
capture_output=True)
print(output)
However, I'm getting an error that the directory cannot be accessed:
CompletedProcess(args=['sudo', 'chown', '-R', 'user:group', '/var/lib/method_transform/data/*'], returncode=1, stdout='', stderr='chown: cannot access ‘/var/lib/method_transform/data/*’: No such file or directory\n')
I tried running the following command from a bash shell script and it worked fine.
sudo chown -R user:group /var/lib/method_transform/data/*
I expect the ownership of all the files to be changed to "user:group"

No such file or directory on Mac terminal for python

hello.py is my first python program. It is saved on my desktop.
In the terminal I write in front of
user#AA-MacBook-Air ~ % python3 hello.py
The error is
can't open file 'hello.py': [Errno 2] No such file or directory
Kindly help me understand the problem and solve it.

In the terminal you are currently in the directory ~. This signifies the folder /Users/<username>. Your script is on your desktop.
Type cd Desktop to change to /Users/<username>/Desktop and then run python3 hello.py.

you first need to change destination with cd

The error message, No such file or directory pretty much gives the explanation. Check if the file hello.py is present in the correct working directory. This can done graphically or using the ls command. If it is not present, copy the file the to the directory or navigate to the location of the file hello.py in terminal using cd.

Makefile on Windows 10 - file not found

After some time I finally managed to successfully install python and pip and run it on my machine using Visual Studio Code.
I am working in virtual environment in python and we have a Makefile with following statement:
test:
source .env && PYTHONPATH=. PY_ENV=testing py.test ${ARGS} --duration=20
File .env lives in the main directory next to Makefile. It contains some environmental variables needed for testing certain APIs.
When I take the line out of the file and run it in my terminal, everything works fine and all tests are running etc.
However if I call the following: make test I am getting this error:
$ make test
source .env && PYTHONPATH=. PY_ENV=testing py.test --duration=20
/usr/bin/sh: line 0: source: .env: file not found
make: *** [test] Error 1
(venv)
To me it looks like when running this command from within Makefile it can't see the .env file but have no idea how to solve it.

The source command isn't looking up the file in the current working directory. As mentioned in man source:
Read and execute commands from filename in the current shell
environment and return the exit status of the last command executed
from filename. If filename does not contain a slash, filenames in
PATH are used to find the directory containing filename.
Change the file path like so:
test:
source ./.env && PYTHONPATH=. PY_ENV=testing py.test ${ARGS} --duration=20
Note that this error does not occur in bash version < 4. This is due to an implementation bug when run under POSIX mode (what make uses, since its default shell is sh, which is usually bash --posix). The correct behaviour was first mentioned in the documentation of bash-2.05 (revision 28ef6c31, file doc/bashref.info):
When Bash is not in POSIX mode, the current directory is searched if
FILENAME is not found in `$PATH'.
These older versions searched the current directory regardless of POSIX mode. It was only in bash-4.0-rc1 (revision 3185942a, file general.c) that this was corrected. Running git diff 3185942a~ 3185942a general.c outputs this section:
## -69,6 +69,7 ## posix_initialize (on)
if (on != 0)
{
interactive_comments = source_uses_path = expand_aliases = 1;
+ source_searches_cwd = 0;
}

Run python module from command line

I don't really know how to ask this question but I can describe what I want to achieve. I would update any edits that would be suggested.
I have a python module that makes use of some command line arguments. Using the module requires some initial setup outside of the python interpreter. The python file that does the setup runs fine, but the problem is that I have to dig through the python installation to find where that file is located i.e. I have to do python full-path-to-setup-script.py -a argA -b argB etc.I would like to call the setup script like this
some-setup-command -a argA -b argB etc.
I want to achieve something like
workon environmnent_name as in the virtualenv module or
pipenv install as in the pipenv module.
I know both of the above commands call a script of some kind (whether bash or python). I've tried digging through the source codes of virtualenv and pipenv without any success.
I would really appreciate if someone could point me to any necessary resource for coding such programs.

If full-path-to-setup-script.py is executable and has a proper shebang line
#! /usr/bin/env python
then you can
ln -s full-path-to-setup-script.py ~/bin/some-command
considering ~/bin exists and is in your PATH,
and you'll be able to invoke
some-command -a argA -b argB

It's a bit difficult to understand what you're looking for, but python -m is my best guess.
For example, to make a new Jupyter kernel, we call
python -m ipykernel arg --option --option
Where arg is the CLI argument and option is a CLI option, and ipykernel is the module receiving the args and options.

Commands that are callable from the command prompt are located in one of the directories in your system's PATH variable. If you are on Windows, you see the locations via:
echo %PATH%
Or if you want a nicer readout:
powershell -c "$env:path -split(';')"
One solution is to create a folder, add it to your system's PATH, and then create a callable file that you can run. In this example we will create a folder in your user profile, add it to the path, then create a callable file in that folder.
mkdir %USERPROFILE%\path
set PATH=%PATH%%USERPROFILE%\path;
setx PATH %PATH%
In the folder %USERPROFILE%\path, we create a batch file with following content:
# file name:
# some-command.bat
#
python C:\full\path\to\setup-script.py %*
Now you should be able to call
some-command -a argA -b argB
And the batch file will call python with python script and pass the arguments you added.

Looking at the above answers, I see no one has mentioned this:
You can of course compile the python file and give executable permissions with
chmod +x filename.py
and then run it as
./filename.py -a argA -b argB ...
Moreover, you can also remove the extention .py (since it is an executable now) and then run it only as
./filename -a argA -b argB ...

run a python script in terminal without the python command

I have a python script let's name it script1.py. I can run it in the terminal this way:
python /path/script1.py
...
but I want to run like a command-line program:
arbitraryname
...
how can i do it ?

You use a shebang line at the start of your script:
#!/usr/bin/env python
make the file executable:
chmod +x arbitraryname
and put it in a directory on your PATH (can be a symlink):
cd ~/bin/
ln -s ~/some/path/to/myscript/arbitraryname

There are three parts:
Add a 'shebang' at the top of your script which tells how to execute your script
Give the script 'run' permissions.
Make the script in your PATH so you can run it from anywhere.
Adding a shebang
You need to add a shebang at the top of your script so the shell knows which interpreter to use when parsing your script. It is generally:
#!path/to/interpretter
To find the path to your python interpretter on your machine you can run the command:
which python
This will search your PATH to find the location of your python executable. It should come back with a absolute path which you can then use to form your shebang. Make sure your shebang is at the top of your python script:
#!/usr/bin/python
Run Permissions
You have to mark your script with run permissions so that your shell knows you want to actually execute it when you try to use it as a command. To do this you can run this command:
chmod +x myscript.py
Add the script to your path
The PATH environment variable is an ordered list of directories that your shell will search when looking for a command you are trying to run. So if you want your python script to be a command you can run from anywhere then it needs to be in your PATH. You can see the contents of your path running the command:
echo $PATH
This will print out a long line of text, where each directory is seperated by a semicolon. Whenever you are wondering where the actual location of an executable that you are running from your PATH, you can find it by running the command:
which <commandname>
Now you have two options: Add your script to a directory already in your PATH, or add a new directory to your PATH. I usually create a directory in my user home directory and then add it the PATH. To add things to your path you can run the command:
export PATH=/my/directory/with/pythonscript:$PATH
Now you should be able to run your python script as a command anywhere. BUT! if you close the shell window and open a new one, the new one won't remember the change you just made to your PATH. So if you want this change to be saved then you need to add that command at the bottom of your .bashrc or .bash_profile

Add the following line to the beginning script1.py
#!/usr/bin/env python
and then make the script executable:
$ chmod +x script1.py
If the script resides in a directory that appears in your PATH variable, you can simply type
$ script1.py
Otherwise, you'll need to provide the full path (either absolute or relative). This includes the current working directory, which should not be in your PATH.
$ ./script1.py

You need to use a hashbang. Add it to the first line of your python script.
#! <full path of python interpreter>
Then change the file permissions, and add the executing permission.
chmod +x <filename>
And finally execute it using
./<filename>
If its in the current directory,