Directories in Verilog

Here’s an idiomatic Verilog example that demonstrates working with directories:

`timescale 1ns / 1ps

module file_operations;

  // File handle
  integer file_handle;
  
  // String to store file names
  reg [100*8-1:0] file_name;
  
  initial begin
    // Create a new directory
    $system("mkdir test_dir");
    
    // Change to the new directory
    $chdir("test_dir");
    
    // Create and write to a file
    file_handle = $fopen("test_file.txt", "w");
    $fwrite(file_handle, "Hello, Verilog!\n");
    $fclose(file_handle);
    
    // List directory contents
    $display("Directory contents:");
    file_handle = $fopen(".|*", "r");
    while ($fscanf(file_handle, "%s\n", file_name) == 1)
      $display("  %s", file_name);
    $fclose(file_handle);
    
    // Read from the file
    $display("\nFile contents:");
    file_handle = $fopen("test_file.txt", "r");
    while (!$feof(file_handle)) begin
      $fgets(file_name, file_handle);
      $write("%s", file_name);
    end
    $fclose(file_handle);
    
    // Change back to the parent directory
    $chdir("..");
    
    // Remove the directory and its contents
    $system("rm -rf test_dir");
  end

endmodule

This Verilog code demonstrates working with directories and files using system tasks and functions. Here’s an explanation of the code:

1. We define a module called file_operations.

2. We declare an integer file_handle to store file descriptors and a 100-character wide register file_name to store file names.

3. In the initial block, we perform various file and directory operations:

   • Create a new directory using the $system task to execute the “mkdir” command.
   • Change to the new directory using $chdir.
   • Create and write to a file using $fopen, $fwrite, and $fclose.
   • List directory contents using $fopen with a wildcard pattern and $fscanf to read file names.
   • Read from the file we created using $fopen, $feof, and $fgets.
   • Change back to the parent directory.
   • Remove the directory and its contents using the $system task.

To run this Verilog code:

1. Save the code in a file with a .v extension (e.g., file_operations.v).
2. Use a Verilog simulator like Icarus Verilog or ModelSim to compile and run the code.

For example, with Icarus Verilog:

$ iverilog -o file_operations file_operations.v
$ vvp file_operations

This will execute the Verilog code and display the output of the directory listing and file contents.

Note that Verilog’s file and directory operations are primarily used for simulation and may not be synthesizable for actual hardware. In real hardware designs, file operations are typically handled by testbenches or external systems interfacing with the hardware.