Execing Processes in Modelica

Here’s the translation of the Go code to Modelica, formatted in Markdown suitable for Hugo:

Our example demonstrates how to execute external processes in Modelica. This is useful when we need to replace the current Modelica process with another (possibly non-Modelica) one.

model ExecingProcesses
  import Modelica.Utilities.System;
  import Modelica.Utilities.Strings;
  
  function executeCommand
    input String command;
    output Integer result;
  algorithm
    result := System.command(command);
  end executeCommand;
  
equation
  when initial() then
    // For our example, we'll execute the 'ls' command
    // Modelica doesn't have a direct equivalent to exec.LookPath,
    // so we assume 'ls' is in the system path
    
    // Prepare the command with arguments
    // Note: In Modelica, we pass arguments as a single string
    command = "ls -a -l -h";
    
    // Execute the command
    result = executeCommand(command);
    
    if result <> 0 then
      Modelica.Utilities.Streams.print("Error executing command. Exit code: " + String(result));
    end if;
  end when;
end ExecingProcesses;

In this Modelica implementation:

1. We import necessary Modelica utilities for system commands and string operations.

2. We define a function executeCommand that wraps the System.command function, which is Modelica’s way of executing system commands.

3. In the initial() event, we prepare the command string. Unlike Go, Modelica doesn’t separate the command and its arguments, so we combine them into a single string.

4. We execute the command using our executeCommand function.

5. We check the result of the command execution. If it’s non-zero, we print an error message.

When we run this model, it will execute the ls -a -l -h command, which lists files in the current directory with additional details.

Note that Modelica’s approach to executing system commands is more limited compared to Go’s. Modelica doesn’t offer fine-grained control over process execution or environment variables. The System.command function is a simpler, higher-level interface for running system commands.

Also, Modelica doesn’t have a concept similar to Go’s process replacement with syscall.Exec. The executed command runs as a separate process, and control returns to the Modelica program after the command completes.

To run this Modelica code, you would typically use a Modelica simulation environment or compiler, which would handle the execution of the model and any system commands it contains.