A Command Line Interface (CLI) is a text-based interface that allows users to interact with a computer by typing commands. Unlike Graphical User Interfaces (GUI), which rely on visual elements, a CLI requires users to enter text commands to perform tasks. This enables the use of the CLI in scripts for system administration, programming, and software development.

Each line of a command line can be decomposed in several parts

Prompt Command Parameters1 ... ParametersN

• The prompt is given by the shell or terminal you are using, for example in the terminal in vscode it is something like this:

username:path$
```

• The command is the program you are executing, for example to compile the project we use maven whose command is mvn, to launch a java program we use java.
• The parameters or arguments are values that are transmitted to the program to parametrize its execution. The parameters depend on the command used (e.g. the parameter for mvn are not the same as the parameter for the java command). Parameters can either be options or arguments.
  • Options modify the behavior of a command. They are preceded by a hyphen (-) and can be single-letter or full words. Some options take a parameters.
  • Arguments are the inputs provided to a command. They can be filenames, directories, or other data needed for the command to operate on.

Example to compile and execute the pandora project from the command line:

$ mvn -B --file pom.xml package

the first line call the program mvn which is the CLI for maven (Maven is a software project management tool by Apache that manage a project's build, reporting and documentation from a single project object model (POM)). We gave to mvn two options -B (batch) and --file pom.xml and one argument package.

the man for the mvn command explain what each of this options does, it also tell us that the last argument is the goal (here: package - Compile and package the compiled code in its distributable format, such as a jar)

Example to call your pandora program:

$ java -jar target/pandora.jar
$ java -jar target/pandora.jar --version

the java command launches a java program, the -jar instruct the command that the main class is in the given.jar file (here target/pandora.jar) all the remaining arguments are given to the target java program (--version is an argument to your pandora program and not to the java command)

to make it clearer we can use an alias to rename java -jar target/pandora.jar to pandora

$ alias pandora='java -jar target/pandora.jar'
$ pandora --version

Options in the command line are flags or switches that modify the behavior of a command. They can be categorized into short options (single-character) and long options (multi-character). Options can sometimes take parameters to provide additional information to the command.

Short options consist of a single character preceded by a hyphen (-). They are often used for quick, one-character modifications.

Example:

$ ls -l

In this example, the -l option is used with the ls command to display detailed information about files and directories.

short options that don't take a parameters can be combined

Example:

$ ls -al
$ ls -a -l

Long options are more descriptive and consist of multiple characters preceded by two hyphens (--). They provide a clearer understanding of their purpose.

Example:

$ git commit --message "Fix bug in feature X"

Here, the --message option is used with the git commit command to include a specific commit message.

Some options require additional parameters to provide more specific information. These parameters are specified immediately after the option.

Example:

$ curl -o output.txt https://example.com/file.txt

In this command, the -o option is used to specify the output file (output.txt) for the data retrieved by the curl command.

for pandora

Arguments in the command line are inputs provided to a command to perform a specific operation. They follow the command and options.

Example:

$ cp file1.txt directory/

In this example, file1.txt and directory/ are arguments for the cp (copy) command. The command copies file1.txt to the specified directory.

for pandora the arguments are either the Flight-Records to parse or one folder that contain the Flight-Records

$ pandora test/resources/0_201_MiG-23MLD.frd
$ pandora test/resources/0_201_MiG-23MLD.frd test/resources/0_301_Su-25T.frd
$ pandora test/resources

you can use the library getopt to ease the development process:

Here is a basic example of using Getopt:

 Getopt g = new Getopt("testprog", argv, "ab:c::d");
 //
 int c;
 String arg;
 while ((c = g.getopt()) != -1)
   {
     switch(c)
       {
          case 'a':
          case 'd':
            System.out.print("You picked " + (char)c + "\n");
            break;
            //
          case 'b':
          case 'c':
            arg = g.getOptarg();
            System.out.print("You picked " + (char)c + 
                             " with an argument of " +
                             ((arg != null) ? arg : "null") + "\n");
            break;
            //
          case '?':
            break; // getopt() already printed an error
            //
          default:
            System.out.print("getopt() returned " + c + "\n");
       }
   }