simple_shell

Objectives

• Write a simple UNIX command interpreter
• Learn about the history of UNIX, shell versions, B language, Ken Thompson; How a shell works; What is a process, pid, and ppid; functions vs system calls; How to manipulate the environment of a process; How shell uses PATH; How to use execve; What is EOF

Features

• man page
• handles semi-columns, pipes, redirections
• handles arguments
• handles errors
• handles end-of-file condition
• handles the PATH
• basic implementation of exit (no arguments)
• handles Ctrl+C
• implements env built-in
• setenv and unsetenv builtins
• future features TBD

System and Environment

• Compiler: gcc 4.8.4
• Tested on Ubuntu 14.04 LTS using Vagrant in VirtualBox

Installation

• Clone the repository: git clone https://github.com/Vilyanare/simple_shell.git
• Change into the proper directory: cd simple_shell
• Compile using: gcc -Wall -Werror -Wextra -pedantic *.c -o hsh
• Run in interactive mode: ./hsh

Usage Example

vagrant@vagrant-ubuntu-trusty-64:~/simple_shell$ ./hsh
$ ls -la
total 92
drwxrwxr-x  4 vagrant vagrant  4096 Nov 20 07:34 .
drwxr-xr-x 11 vagrant vagrant  4096 Nov 20 01:16 ..
-rw-rw-r--  1 vagrant vagrant   144 Nov 20 07:29 AUTHORS
-rw-rw-r--  1 vagrant vagrant  1130 Nov 19 23:31 built_ins.c
-rw-rw-r--  1 vagrant vagrant  1675 Nov 19 23:31 envlistfunc.c
-rw-rw-r--  1 vagrant vagrant  3201 Nov 18 02:39 _eprintf.c
drwxrwxr-x  8 vagrant vagrant  4096 Nov 20 07:35 .git
-rw-rw-r--  1 vagrant vagrant    39 Nov 15 23:55 .gitignore
-rwxrwxr-x  1 vagrant vagrant 18692 Nov 20 03:21 hsh
-rw-rw-r--  1 vagrant vagrant  1484 Nov 20 07:24 man_1_simple_shell
-rw-rw-r--  1 vagrant vagrant  1195 Nov 19 23:31 path.c
-rw-rw-r--  1 vagrant vagrant  3183 Nov 15 22:19 _printf.c
-rw-rw-r--  1 vagrant vagrant  2364 Nov 20 07:34 README.md
-rw-rw-r--  1 vagrant vagrant  3189 Nov 19 23:31 shell.h
-rw-rw-r--  1 vagrant vagrant  1098 Nov 20 01:51 simple_shell.c
-rw-rw-r--  1 vagrant vagrant  1363 Nov 18 02:39 strings1.c
-rw-rw-r--  1 vagrant vagrant  3032 Nov 19 23:31 strings2.c
-rw-rw-r--  1 vagrant vagrant  1099 Nov 19 23:31 strings3.c
$ exit
vagrant@vagrant-ubuntu-trusty-64:~/simple_shell$

File Descriptions

---

File	Description
_eprintf.c	a custom printf() that prints to standard error
_printf.c	a custom verson of printf() that handles string and int
built_ins.c	enables the shell to execute certain custom built-ins
changeenv.c	allows changes to be made to the environment
envlistfunc.c	contains functions for manipulating env as a linked list
man_1_simple_shell	a man page for hsh
path.c	enables the creation and searching of PATH
shell.h	contains directives, libraries, structures, and function prototypes
simple_shell.c	the main file that executes the shell
strings1.c	custom versions of strcpy, strlen, puts, strchr, strdup
strings2.c	custom versions of strcat, realloc, strtok, and tokenizer-related functions
strings3.c	custom versions of strcmp and atoi
Files not described: .gitignore, AUTHORS, README.md

Constraints

• No more than 5 functions per file
• Program must have the exact same output as sh (/bin/sh)
• Betty styling
• Only certain functions were allowed; many STL functions were recreated
• Those functions allowed are: access, chdir, close, closedir, execve, exit, fork, free, stat, lstat, fstat, getcwd, getline, kill, malloc, open, opendir, perror, read, readdir, signal, strtok, wait, waitpid, wait3, wait4, write, _exit, isatty, fflush

Authors

• Thomas Dumont - github: vilyanare
• Jacob Hartman - github: JacobBHartman