Useless Shell

GitHub Repo

A shell written in C with no purpose. However, it was fun to write.

Welcome, Guest.                              
                                             
Today is Fri Oct 11 09:54:10 2024.           
> help                                       
- exit                                       
- help (cmd) -b                              
- clear                                                
- history                                              
  Display the session command history                  
  - clear                                              
- login <username>                                     
  Login to an existing account                         
- logout                                               
  Logout of the currect account                        
- users                                                
  - info (username)                                    
  - list                                               
  - create <username> <password> (super)               
  - delete <username>                                  
- uninstall                                            
- time -d -w                                           
  Shows system time                                    
> users list                                           
1       [@] admin                                      
> time -d                                              
 _   _     __  __   __  _                              
| | |_| ' |_  |_  '  _|  |                             
|_| __| . __| __| . |__ _|_                            
>

Features

• Command auto completion (Tab)
• Command syntax hints (Ctrl+Tab)
• List commands with help
• Colorful!

• Users

  • Saved to file
  • Password hashing using the RSA Data Security, Inc. MD5 Message Digest Algorithm
  • Superusers

• History

  • Saved to file per user (& guest)
  • View with history
  • Clear with history clear
  • Navigation (↑ & ↓)
• Easy command declaration (see cmd_defs.c)
• Command verification and unit testing

• Input buffer editing

  • Cursor navigation (← & →)
  • Word navigation (Ctrl+← & Ctrl+→)
  • Backspace & Back word (Ctrl+Backspace)
  • Delete & Delete word (Ctrl+Del)
  • Clear (escape)
• Easy uninstallation: login as admin and run uninstall.
• Portable (ish): Single executable file and config directory.

Installation

Download the latest release or build from source with CMake.

Note that a config directory is placed at:

Run the executable and enter a password for the new admin user.

Adding a new command

1. Add definition to cmd_defs.c

   Use the CMD macro with named-member-initalization style for name, description, type, optional, impl, and auto_complete.
   name and type are required, while the others are optional.

   Valid types must be prefixed with USCommandArgType and are as follows:
   Number, String, Secret, Boolean, and Flag.

   When type is Flag, optional and auto_complete are ignored.

   impl describes the implementation. Set it to the CMD_IMPL macro

   Example

   CMD(
       .name = "history",
       .description = "Display the session command history",
       .impl = CMD_IMPL(history),
       SUB_CMDS(
           CMD(
               .name = "clear",
               .impl = CMD_IMPL(history_clear)
           )
       )
   )

2. Add implementation declaration to cmd_impl.h

   Call the CMD_IMPL_PROTO with the implementation name you chose in the previous step.

   Example

   CMD_IMPL_PROTO(history);

3. Add implementation to cmd_impl.c
   Example

   CMD_IMPL_PROTO(history)
   {
       // Information about the shell can be accessed via `us` parameter
       if (fseek(us->history.read, 0, SEEK_SET) == 0)
       {
           ...
       }
       else
       {
           puts(STYLE_ERROR("Failed to read history"));
           return USCommandReturnError;
       }
       return USCommandReturnNormal;
   }

Adding a new auto complete function is very similar, but uses the AC_IMPL and AC_IMPL_PROTO macros instead.