Basic Command Shell

When run, command prompts are printed, and commands are read in from the user one line at a time and executed. This file first outlines how to run the program, gives details on how it works, explains how the cd command is used, what the control-c signal does, and then give the bugs and problems with this programm.

Installation

The following is the instructions for running the command shell

$ git clone  https://github.com/yourusername/rshell.git
$ cd rshell
$ git checkout hw0
$ make
$ bin/rshell

Running make creates the executable and places it into a created directory bin. Running make clean will delete the directory bin and everything in it.

Details

One the program has be run, commands should be given like so

executable [ argumentList ] [ connector command ]

Where connectors can be ;, &&, or ||. The executable is an executable program in the PATH. To exit the program, the user types exit at the beginning of a command. When exit is found, anything following it will not execute. Any single & or | will be ignored. Anything following a # is considered a comment, and thus will be ignored. The directory tests holds a exec.script file with test cases. For connectors, if a command will not be executed due to the connector before it, all other commands after will also not execute. For example

true || ls && pwd

will only execute the first command (here true), but because it suceeded, and thus ls won't be executed, then pwd will also not be executed.

##cd cd is a command built into rshell. This command comes in three formats,

1. cd <PATH> will change the current working directory to <PATH>.

2. cd will change the current working directory to the user's home directory.

3. cd - will change the current working directory to the previous working directory.

If more than one flag is passed in after cd, an error messgae will be printed.

##CONTROL-C When this is pressed, rshell doesn't quit, SIGINT being caught. rshell continues as if you hadn't even pressed control-c. If currently running a program through rshell, the program will recieve the signal, with the program quitting.

##Bugs/Limitations/Issues

1. If the user input has only tabs or spaces before a | or a & at the beginning, before any commands, it causes a segmentation fault and quits the program. examples:

  || ls
 & ps

2. The program will only hold up to 99 arguments for every command.

3. Using cd means the current directory shown by the prompt will be exactly what you type in, even paths such as .. or a folder name, rather than the current directory path from HOME.