• Write and format the code according to the Betty style guide.
• Ensure the code passes all Betty checks.

• Display a prompt and wait for user input.
• Read a command line, ending with a newline character.
• Handle "end of file" condition (Ctrl+D).

• Execute simple commands without arguments.
• Display the prompt after executing a command.
• Handle errors if the executable is not found.

• Modify the shell to handle command lines with arguments.
• Parse and execute commands with provided arguments.
• Display the prompt after executing a command.

• Implement PATH handling to locate executables.
• Check the existence of a command before forking a process.

• Implement the exit built-in command to exit the shell.
• Display an error message if arguments are provided to exit.

• Implement the env built-in command to print the current environment.
• Test the env command in interactive mode.

• Implement a custom getline function.
• Use a buffer to read multiple characters at once.
• Minimize the use of the read system call.
• Use static variables for efficient implementation.

• Implement the shell without using the strtok function.
• Use alternative methods to tokenize input.

• Allow the exit built-in to accept an optional exit status.
• Display an error message if the exit status is not an integer.

• Implement setenv and unsetenv built-in commands.
• setenv initializes or modifies an environment variable.
• unsetenv removes an environment variable.

• Implement the cd built-in command to change the current directory.
• Handle the special case of "cd -" to switch to the previous directory.
• Update the PWD environment variable.

• Implement the command separator (;) to execute multiple commands.

• Implement the && and || logical operators to control command execution.

• Implement the alias built-in command.
• Allow defining, printing, and listing aliases.

• Handle variables replacement in commands.
• Implement $? and $$ variable replacements.

• Handle comments in commands (lines starting with #).

• Modify the shell to accept a file as a command line argument.
• Execute commands from the file one line at a time.
• Do not print a prompt or read from stdin in this mode.

====================================== End of Simple Shell Implementation Workflow