Directories in Pascal

Here’s the translation of the Go code to Pascal, along with explanations in Markdown format suitable for Hugo:

Our program demonstrates working with directories in the file system. Here’s the full source code:

program Directories;

uses
  SysUtils;

procedure Check(E: Exception);
begin
  if E <> nil then
    raise E;
end;

procedure CreateEmptyFile(Name: string);
var
  F: TextFile;
begin
  AssignFile(F, Name);
  Rewrite(F);
  CloseFile(F);
end;

procedure VisitDirectory(const Path: string);
var
  SR: TSearchRec;
begin
  if FindFirst(Path + '\*', faAnyFile, SR) = 0 then
  begin
    try
      repeat
        WriteLn(' ', Path + '\' + SR.Name, (SR.Attr and faDirectory) <> 0);
      until FindNext(SR) <> 0;
    finally
      FindClose(SR);
    end;
  end;
end;

begin
  // Create a new sub-directory in the current working directory
  try
    CreateDir('subdir');
  except
    on E: Exception do
      Check(E);
  end;

  // When creating temporary directories, it's good practice to remove them afterwards
  try
    // Helper function to create a new empty file
    CreateEmptyFile('subdir\file1');

    // We can create a hierarchy of directories, including parents
    ForceDirectories('subdir\parent\child');

    CreateEmptyFile('subdir\parent\file2');
    CreateEmptyFile('subdir\parent\file3');
    CreateEmptyFile('subdir\parent\child\file4');

    // List directory contents
    WriteLn('Listing subdir\parent');
    VisitDirectory('subdir\parent');

    // Change the current working directory
    ChDir('subdir\parent\child');

    // Now we'll see the contents of subdir\parent\child when listing the current directory
    WriteLn('Listing subdir\parent\child');
    VisitDirectory('.');

    // Change back to where we started
    ChDir('..\..\..');

    // We can also visit a directory recursively, including all its sub-directories
    WriteLn('Visiting subdir');
    VisitDirectory('subdir');

  finally
    // Remove the entire directory tree
    RemoveDir('subdir');
  end;
end.

To run the program, save it as directories.pas and compile it using a Pascal compiler like Free Pascal:

$ fpc directories.pas
$ ./directories

This program demonstrates several operations on directories:

Creating directories using CreateDir and ForceDirectories.
Creating empty files in these directories.
Listing directory contents using FindFirst, FindNext, and FindClose.
Changing the current working directory with ChDir.
Recursively visiting directories.
Cleaning up by removing the entire directory tree.

Note that Pascal doesn’t have built-in functions for some operations that are available in more modern languages. We’ve simulated these using combinations of available functions and procedures.

The VisitDirectory procedure demonstrates how to recursively list directory contents in Pascal. It’s a simplified version of the WalkDir functionality shown in the original example.

Remember to handle exceptions properly in a real-world application, especially when dealing with file system operations that can fail due to permission issues or other system-level problems.

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