minishell

#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# Minimal Shell
#    Use whenever a user should be able to launch a shell,
#    but not to execute commands.
#

# Backwards compatibility with Python 2
try:
    input = raw_input
except NameError:
    pass

import platform
from getpass import getuser
import os

def main():
    commands_allowed = (
        "",
        "exit",
        "logout",
        "help",
        "whoami",
        "id",
        "hostname",
        "pwd",
        "bash",
        "uname",
        "clear"
    )
    command = ""
    print("""
This is Minimal Shell on node """+platform.node()+""".

Type exit<ENTER> to exit.
""")
    
    try:
        while command != "exit":
            print("$ ",end="")
            try:
                command = input()
            except KeyboardInterrupt:
                print("")
                continue
            if command == "logout":
                command = "exit"
            elif command == "help":
                print("""Minimal Shell Help
Commands:
    whoami
    hostname
    pwd
    uname
    clear
    help
    logout/exit
""")
            elif command == "whoami":
                print(getuser())
            elif command == "id":
                print("uid=42("+getuser()+") gid=100(users) groups=42("+getuser()+"),9999(minishell)")
            elif command == "hostname":
                print(platform.uname()[1])
            elif command == "pwd":
                print("/usr/home/"+getuser())
            elif command == "bash":
                print("Executing bash session...")
                ret_code = os.system("bash")
                if ret_code != 0:
                    print("bash session exited with non-zero code "+str(ret_code)+".")
            elif command == "uname":
                print(platform.uname()[0]+" "+platform.uname()[1]+" "+platform.uname()[2])
            elif command == "clear":
                ret_code = os.system("clear")
            if not command in commands_allowed:
                if os.system("which " + command.split()[0] + " &>/dev/null") == 0:
                    print("-minishell: "+command.split(" ")[0]+": You may not execute commands!")
                else:
                    print("-minishell: "+command.split(" ")[0]+": Command not found.")
    except EOFError:
        print("<EOF>")
    print("Good bye.")

if __name__ == "__main__":
    main()