Need to lock MODFLOW output files when they are loaded in model viewer

[scharlton2]

See #66.

from chatGPT:

How do I lock a file so that no other programs can write to it?
There are a few ways to lock a file so that no other programs can write to it.

Using the file's properties: Depending on the operating system, you can use the file's properties to set it as read-only. This will prevent other programs from making changes to the file.

Using a third-party software: There are various third-party software available that allows you to lock files and folders, and set permissions for different users or programs.

Using command line: In windows, you can use the command "icacls" to set specific permissions on a file or folder, and also, "attrib +r" will set the read-only attribute on a file.
In Linux, you can use the command "chmod" to set specific permissions on a file or folder, and also, "chattr +i" will set the immutable attribute on a file.

It's important to note that while these methods can prevent other programs from making changes to the locked file, they will not prevent a user with administrative access from modifying the file.

How do I do it in c++?
In C++, you can use the "chmod" function to set specific permissions on a file. The "chmod" function is part of the "sys/stat.h" header file, which you will need to include in your program.

Here is an example of how you can use the "chmod" function to set the read-only permission on a file:

#include <iostream>
#include <sys/stat.h>

using namespace std;

int main() {
    // File path
    string filePath = "example.txt";

    // Set read-only permission (444)
    chmod(filePath.c_str(), S_IRUSR | S_IRGRP | S_IROTH);

    cout << "File set to read-only" << endl;

    return 0;
}

In this example, the "chmod" function is used to set the read-only permission (444) on a file called "example.txt". The file path is passed to the function as a C-style string using the "filePath.c_str()" method.

It's important to note that the above code will only set the read-only permissions for the current user, for other users or groups, you will need to add the relevant flags.

Also, it's possible that the chmod will not work in certain operating systems, you can use the _wchmod in windows to change the permissions of a file.

Keep in mind that you need administrative access to change the permissions of a file.

wouldn't the other process be able to call chmod and make it writeable?
Yes, that's correct. If another process has administrative access, it can change the permissions on the file and make it writable again.

Locking a file in a way that can't be overridden by another process with administrative access is a difficult task, because it would involve some sort of security feature that could only be implemented at the operating system level.

A common alternative is to use a file-locking mechanism provided by the operating system. For example, in Windows you can use the LockFileEx and UnlockFileEx functions, and in Linux you can use the flock function. These functions provide a way to lock a file for exclusive access by a single process, and can be used to prevent other processes from writing to the file while it is locked.

Another option is to use a third-party library that provide a more robust file-locking system.
Keep in mind that locking a file only ensures that no other process can modify it while it's locked, but it doesn't guarantee data consistency, for example, if a process crash while it's holding the lock, the file might be left in an inconsistent state.

How could it be done on macos?
On macOS, you can use the "chflags" command in the Terminal to set the "uchg" flag on a file, which makes it immutable and prevents any changes from being made to the file. This flag can only be unset by a user with root privileges.

Here's an example of how you can use the "chflags" command to make a file immutable:

chflags uchg /path/to/file

You can check if a file is immutable by running the command ls -lO /path/to/file and looking for "uchg" in the flags.

You can also use the chflags command to remove the immutable flag by calling

chflags nouchg /path/to/file

Keep in mind that like in other operating systems, making a file immutable only ensures that no other process can modify it while it's locked, but it doesn't guarantee data consistency, for example, if a process crash while it's holding the lock, the file might be left in an inconsistent state.

Also, even if the file is immutable, users with root privileges can still modify the file.

Another option is to use a third-party library that provide a more robust file-locking system.

Does macos have the flock functionality?
Yes, macOS does have the flock functionality. The "flock" function is a POSIX-compliant function that is available on macOS, as well as many other Unix-like operating systems.

The flock function can be used to lock a file for exclusive access by a single process, and can be used to prevent other processes from writing to the file while it is locked. Here's an example of how you can use the flock function to lock a file:

#include <sys/file.h>

int fd = open("/path/to/file", O_RDONLY);

int result = flock(fd, LOCK_EX);
if (result == 0) {
    // File locked successfully
    // Perform operations on the file
    // ...

    flock(fd, LOCK_UN);
} else {
    // Failed to lock the file
    // Handle the error
    // ...
}

close(fd);

In this example, the "flock" function is used to acquire an exclusive lock on the file, represented by the file descriptor "fd", and LOCK_EX flag. Once the operations on the file are done, the lock is released by calling flock with LOCK_UN flag.

It's important to note that while the flock function provides a way to lock a file for exclusive access by a single process, it doesn't guarantee data consistency, for example, if a process crash while it's holding the lock, the file might be left in an inconsistent state.

Another option is to use a third-party library that provide a more robust file-locking system.

Could this be done using the Qt framework?
Yes, it's possible to lock a file using the Qt framework. One way to accomplish this is by using the QFile class, which provides a way to read and write files, and the QLockFile class, which provides a platform-independent way to lock a file for exclusive access by a single process.

Here's an example of how you can use the QLockFile class to lock a file:

#include <QLockFile>

QLockFile lockFile("/path/to/file");

if (lockFile.tryLock()) {
    // File locked successfully
    // Perform operations on the file
    // ...
    lockFile.unlock();
} else {
    // Failed to lock the file
    // Handle the error
    // ...
}

In this example, the QLockFile object is created and passed the path to the file to be locked, then the tryLock method is called to attempt to lock the file. If the lock is acquired, the lock can be released using the unlock() method.

It's important to note that while the QLockFile class provides a way to lock a file for exclusive access by a single process, it doesn't guarantee data consistency, for example, if a process crash while it's holding the lock, the file might be left in an inconsistent state.

Another option is to use a third-party library that provide a more robust file-locking system.

Qt provides a lot of functionality to work with files and their access, you can use the QFile class to read, write and access the file, and the QLockFile class to lock the file, it's a platform-independent way that abstracts the system-specific way of locking files.