Clarification of Rust File Paths and access - rust

Very new to Rust and am looking for clarification about rust file paths that are outside the project directory. I would expect reading a .txt file from say the desktop to look something roughly like this:
fs::read_to_string("./Desktop/test.txt");
However, this does not seem to work. Is this an issue with the file path listed or does Rust only allow access to files in the project directory? If this is the default case how does one allow access to files elsewhere in the system outside the current working directory?
Say the project is in Documents and we want to access some text file on the Desktop.
Found the answer, seems the path that I am looking for is like this :
fs::read_to_string("/Desktop/test.txt");
Seems the "." was looking in the current directory.


When you open a path that starts with ./, it is relative to the current working directory.
Assuming that the program does not change the working directory itself, that would be whatever directory the user was in when they started the executable.
Note that it is not necessarily the project directory: when you are developing your program, you will probably run it via cargo run, but when it is ready you would most likely copy the target executable into a directory that is in the path. The working directory can be completely different to the directory in which the executable is placed.
Your program can find out the current working directory by calling std::env::current_dir
If you want a path that does not depend on the working directory, you can use an absolute path, ie. starting with /.
Rust is no different to any other programming language in this respect. In particular, files are not opened in respect to the project dir.


As specified, the path will be relative to the working directory of the process. If the working directory isn't your home directory, then you need to be more specific about where the file is.
Note that the working directory can change depending on how you run the program. The link above has more information on this topic.
You can obtain your user's desktop directory using desktop_dir from the dirs crate, which will make the working directory irrelevant in this particular case. It will also correctly determine the user's desktop directory on many different operating systems.
fs::read_to_string({
let mut path = dirs::desktop_dir().expect("no desktop directory");
path.push("test.txt");
path
})

Related

How to reference or link files and folders inside a git repository to match these criteria?

I've encountered a problem long time ago which I couldn't solve, but I'm curious whether it's possible to fulfill ALL of the below listed criteria at once or not.
The solution what I was looking for can:
somehow refer to an existing file or folder from another folder of the same git repo
basically reach the content of the file or folder from another subfolder, see the content(s) as if they were on the another path as well
e.g.: if ./path/to/folder is referred from ./another_path/different_folder, then every file in ./path/to/folder/* is visible on path ./another_path/different_folder/*
e.g.: if ./path/to/file is referred by ./another_path/different_file, then by reading/writing content of the different_file, the original file is read/modified
store the referred file only once in git repo
don't want to make a copy of the file to another path and maintain changes in both files simultaneously
be able to use multiple references for a single file
be able to use relative paths
make it work on both Windows and Linux
As if I can remember, some of the problems were while experimenting with this:
the paths were broken after the repository was pulled to a different path (I assume they were not relative, but absolute)
the Windows style links are special files, were not working on Linux
the symlinks can't handle relative paths correctly on the Windows system
the hardlinks resulted duplicating files in Windows
(I can't remember exactly which if these might be incorrect, but I'll experiment with the problem again and try to update this question.)
Is there any workaround for this problem?
Thank you for any help!
Please note (in case you would like to mark this question as a duplicate), that there are other similar questions here, but none of those questions define this set of the criteria, therefore it can't be a duplicate.

PyCharm project path different from interactive session path

When running an interactive session, PyCharm thinks of os.getcwd() as my project's directory. However, when I run my script from the command line, PyCharm thinks of os.getcwd() as the directory of the script.
Is there a good workaround for this? Here is what I tried and did not like:
going to Run/Edit Configurations and changing the working directory manually. I did not like this solution, because I will have to do it for every script that I run.
having one line in my code that "fixes" the path for the purposes of interactive sessions and commenting it out before running from command line. This works, but feels wrong.
Is there a way to do this or is it just the way it is supposed to be? Maybe I shouldn't be trying to run random scripts within my project?
Any insight would be greatly appreciated.
Clarification:
By "interactive session" I mean being able to run each line individually in a Python/IPython Console
By "running from command line" I mean creating a script my_script.py and running python path_to_myscript/my_script.py (I actually press the Run button at PyCharm, but I think it's the same).
Other facts that might prove worth mentioning:
I have created a PyCharm project. This contains (among other things) the package Graphs, which contains the module Graph and some .txt files. When I do something within my Graph module (e.g. read a graph from a file), I like to test that things worked as expected. I do this by running a selection of lines (interactively). To read a .txt file, I have to go (using os.path.join()) from the current working directory (the project directory, ...\\project_name) to the module's directory ...\\project_name\\Graphs, where the file is located. However, when I run the whole script via the command line, the command reading the .txt file raises an Error, complaining that no file was found. By looking on the name of the file that was not found, I see that the full file name is something like this:
...\\project_name\\Graphs\\Graphs\\graph1.txt
It seems that this time the current working directory is ...\\project_name\\Graphs\\, and my os.path.join() command actually spoils it.

I user various methods in my python scripts.
set the working directory as first step of your code using os.chdir(some_existing_path)
This would mean all your other paths should be referenced to this, as you hard set the path. You just need to make sure it works from any location and your specifically in your IDE. Obviously, another os.chdir() would change the working directory and os.getcwd() would return the new working directory
set the working directory to __file__ by using os.chdir(os.path.dirname(__file__))
This is actually what I use most, as it is quite reliable, and then I reference all further paths or file operations to this. Or you can simply refer to as os.path.dirname(__file__) in your code without actually changing the working directory
get the working directory using os.getcwd()
And reference all path and file operations to this, knowing it will change based on how the script is launched. Note: do NOT assume that this returns the location of your script, it returns the working directory of the shell !!
[EDIT based on new information]
By "interactive session" I mean being able to run each line
individually in a Python/IPython Console
By running interactively line-by-line in a Python console, the __file__ is not defined, afterall: you are not executing a file. Hence you cannot use os.path.dirname(__file__) you will have to use something like os.chdir(some_known_existing_dir) to reference a path. As a programmer you need to be very aware of working directory and changes to this, your code should reflect that.
By "running from command line" I mean creating a script my_script.py
and running python path_to_myscript/my_script.py (I actually press the
Run button at PyCharm, but I think it's the same).
This, both executing a .py from command line as well as running in your IDE, will populate the __file__, hence you can use os.path.dirname(__file__)
HTH

I am purposely adding another answer to this post, in regards the following:
Other facts that might prove worth mentioning:
I have created a PyCharm project. This contains (among other things)
the package Graphs, which contains the module Graph and some .txt
files. When I do something within my Graph module (e.g. read a graph
from a file), I like to test that things worked as expected. I do this
by running a selection of lines (interactively). To read a .txt file,
I have to go (using os.path.join()) from the current working directory
(the project directory, ...\project_name) to the module's directory
...\project_name\Graphs, where the file is located. However, when I
run the whole script via the command line, the command reading the
.txt file raises an Error, complaining that no file was found. By
looking on the name of the file that was not found, I see that the
full file name is something like this:
...\project_name\Graphs\Graphs\graph1.txt It seems that this time
the current working directory is ...\project_name\Graphs\, and my
os.path.join() command actually spoils it.
I strongly believe that if a python script takes input from any file, that the author of the script needs to cater for this in the script.
What I mean is you as the author need to make sure you know the following regardless of how your script is executed:
What is the working directory
What is the script directory
These two you have no control over when you hand off your script to others, or run it on other peoples machines. The working directory is dependent on how the script is launched. It seems that you run on Windows, so here is an example:
C:\> c:\python\python your_script.py
The working directory is now C:\ if your_script.py is in C:\
C:\some_dir\another_dir\> c:\python\python.exe c:\your_script_dir\your_script.py
The working directory is now C:\some_dir\another_dir
And the above example may even give different results if the SYSTEM PATH variable is set to the path of the location of your_script.py
You need to ensure that your script works even if the user(s) of your script are placing this in various locations on their machines. Some people (and I don't know why) tend to put everything on the Desktop. You need to ensure your script can cope with this, including any spaces in the path name.
Furthermore, if your script is taking input from a file, the you as the author need to ensure that you can cope with changes in working directory, and changes of script directory. There are a few things you may consider:
Have your script input from a known (static) directory, something like C:\python_input\
Have your script input from a known (configurable) directory, use ConfigParser, you can search here on stackoverflow on many posts
Have your script input from a known directory related to the location of the script (using os.path.dirname(__file__))
any other method you may employ to ensure your script can get to the input
Ultimately this is all in your control, and you need to code to ensure it is working.
HTH,
Edwin.

Which path can i use inside my program that will fit other computers? (that also have ubuntu)

I made a program in QT c++ that creates some files and i want them to be saved in a specific directory, i created a directory and i moved all the program there so i can use that same directory to save them, but when i write the path to save the files i have to write:
/home/"the name of my computer"/my_program/file.txt
and i want to use this same program in different computers. I also tried just writing:
my_program/file.txt
but it doesn't work.

Your relative path approach was already good, but a relative path is treated as relative to the working directory of the process and that depends on how the program is started.
E.g. if you start it from a shell, then the shell's current working directory will be the program's, if you start it from a launcher menu, it is often the user's home directory, but could be the location of the binary, etc.
So it is better to create a path based on well known base paths. such as the user's home directory, see QDir::home() or the a common location depending on type of data, see QStandardPaths

Did you try home directory path with "~/", many applications save their settings in ~/.applicationName directory

where is Qt configuration file (qtrc) on Linux?

I have not found it in:
~/.config/Trolltech
~/.qt
~/.config/Nokia
where I should search for it?

It will depend on your system where exactly to find it. You could try running locate qtrc. Note that the locations this is going to find aren't necessarily the ones where you should make changes -- on my system, I only have a system-wide qtrc in /etc. For local changes, you should add a new one in your home directory. Again the particular location within your home directory will depend on your installation (in particular whether you're using Qt3 or Qt4).

Autotools Home Directory

I want my program to create files at run-time (log files and such), so it needs to know the home directory of the user, or else he/she would have to run the program as root every time (to create the files in directories like /var).
Is there some way to add a -D define in the Makefile.am that is automatically filled with the home directory? For instance I already have AM_CPPFLAGS=-DDATADIR='"$(datadir)"' to define the data directory.

There isn't any macro or built-in path in Autotools, that represent user's home directory, you can obtain it at runtime using (for example) environment variables.
BTW. for logging I recommend syslog() .

Why not use the HOME environment variable for your program instead?

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