slash - a new shell for unix
============================
    ) author    :: brian reily
    ) site      :: brianreily.com/projects/slash 

table of contents
-----------------
    ) why
    ) building
    ) features / functionality
    ) modes
    ) usage
    ) todo / issues
    ) source code

why
---
    ) slash started as a school project that began as a simple
      while loop that passed commands to exec.

    ) i slowly started adding features (aliases, globs, etc) and
      it go to the point where it become a pretty usable shell.

    ) development continues mainly as a learning process, both for
      myself and for others that want to learn how a shell works.  i
      feel the codebase is small enough that its easy to see whats
      going on - one of my main tasks now is adding comments wherever
      possible.
    
    ) slash is not meant as a replacement for bash or zsh, but hacking
      on it greatly increases your understanding of unix.

building
--------
    1) set some options in config.h - you can change most of these later
       in your startup config file or with command line flags, but its 
       easiest to set them now.
    2) make
    3a) ./slash 
    3b) cp slash /bin/; slash
    4) to exit the shell, use 'exit' or 'x'

features / functionality
------------------------
    ) aliases
        > aliases work as in bash - if the first token in a command line is
          an alias, it is expanded to whatever that alias stands for.
        > example:
            ] $ alias lf 'ls -F'    # Aliases 'lf' to 'ls -F'
            ] $ lf                  # Expands to 'ls -F'
        > another example:
            ] $ alias rm 'rm -i'    # Aliases 'rm' to 'rm -i'
            ] $ rm important_file   # Expands to 'rm -i important_file'
        > to see all active aliases, use 'get -aliases'

    ) config files / profiles
        > slash automatically loads a configuration file at startup
        > by default, this is ~/.slash_config
        > this is ideally where you would customize your prompt, aliases,
          settings; source other files; etc.
        > to load a different configuration file at startup, use the -c or
          --config [FILE] options
        > to not load a configuration file at all, use the -nc or --noconfig
          options

    ) globbing / wildcard expressions
        > slash offers globbing with the '*' character
        > example:
            ] $ ls *c *h
            ] aliases.c aliases.h builtins.c builtins.h ...
        > example:
            ] $ ls
            ] projects/ source/
            ] $ cd p*

    ) environment variables
        > slash uses a number of variables
        > variables inside commands will expand:
            ] $ set @dir /Users/brian/code
            ] $ cd {@dir}
        > to get the value of a variable, use 'get [VARIABLE]':
            ] $ get @config
            ] ~/.slash_config
        > to set the value of a variable, use 'set [VARIABLE] [VALUE]':
            ] $ set @config '~/.other_config'
        > to see the values of all shell variables, use 'get -all'    

    ) customizable prompt
        > slash allows a number of useful macros to use in your prompt; to
          see a full listing look in prompt.c or in 'help prompt'
        > example:
            ] $ set @prompt '{pwd}$ '
            ] ~/projects$ set @prompt '{date%H:%M:%S}$ '
            ] 01:05:57$ set @prompt 'hello, {user}$ '
            ] hello, brian$ 
        > the date macro takes the same parameters as the actual 'date'
          shell command - instead of 'date +"%H:%M:%S"', you use 
          {date%H:%M:%S} as the macro.  this accepts anything that the 
          date command accepts.

    ) scripts
        > slash allows you to execute a script of shell commands
        > currently, advanced shell features like loops and conditionals
          are not accepted
        > you can execute scripts using the 'source' command, or by using
          the -s or --script [FILE] command line options
          
    ) redirection of stdin and stdout
        > slash allows you to redirect stdin from a file:
            ] $ cat < a.txt
        > slash allows you to redirect stdout, truncating a file:
            ] $ ls > a.txt
        > slash also allows you to redirect stdout, appending a file:
            ] $ ls >> a.txt
        > you can combine these:
            ] $ head < a.txt > b.txt

    ) pipes
        > pipes are a work in progress

modes
-----
    ) slash offers various modes of operation:
        > normal mode:  this presents the standard shell interaction, where
                     ]  the user is presented with a prompt to type in
                     ]  commands.

        > script mode:  this allows the user to run a script of shell commands,
                     ]  by using the -s or --script command line options.  this
                     ]  mode exits after running the script, unless a -ne or
                     ]  --noexit command line option is included, in which case
                     ]  slash switches to normal mode.

        > command mode: this allows the user to run a single command, by using
                      ] the -e or --execute command line options.  like script
                      ] mode, the shell defaults to exiting afterwards.  the
                      ] command must be surrounded by quotes.

todo / issues
-------------
    ) pipes are the last major/required feature that needs to be added.
      there is code in place for it but it currently doesn't work.
    
    ) comments are going to be added liberally all over the place, both
      for my organization (the code has grown a lot and i haven't been
      able to keep up) and for other people's understanding.
    
    ) using a history file doesn't work right now - it seems as simple as
      calling the history library's function for that but it returns an
      error and doesn't read anything.
    
    ) right now make simply compiles slash; i need to add a 'make install'
      rule

source code
-----------
    1) slash.c
        > location of main()
    
    2) aliases.h / aliases.c
        > set, store and substitute aliases

    3) bg.h / bg.c
        > checks if function should be in the background

    4) builtins.h / builtins.c
        > parse and execute builtin commands

    5) config.h
        > allows you to set a number of options before building

    6) environ.h / environ.c
        > set, get, and store environment variables and settings
    
    7) error.h / error.c
        > handles error message printing for slash

    8) eval.h / eval.c
        > evaluates each command line

    9) globbing.h / globbing.c
        > handles wildcard support for slash

   10) help.h / help.c
        > handles all help and usage commands
    
   11) init.h / init.c
        > handles all setup tasks, before presenting a prompt

   12) input.h / input.c
        > handles both file and command line input

   13) options.h / options.c
        > parses command line flags

   14) parser.h / parser.c
        > splits command lines into arrays of tokens

   15) prompt.h / prompt.c
        > handles printing the prompt and evaluating prompt macros

   16) redirect.h / redirect.c
        > handles io redirection