Simple Shell

Description

This program is a simple Unix shell implemented in C using the gnu89 standard.

The purpose of this project was to demonstrate our (Bezaleel Olakunori & Elmahdi Mamoun) understanding of a variety of programming concepts and low-level system functionalities.

Here's a screenshot of our simple shell in action.

How To Use

Run the command below to build the shell.

gcc -Wall -Werror -Wextra -pedantic -std=gnu89 *.c -o simple_shell

After compiling the program, run ./simple_shell to startup the shell in interactive mode. To start the shell in non-interactive mode, run ./simple_shell file, where file is a text-encoded file containing lines of commands to be executed. You can also pipe a string of commands to the program like echo 'echo $PWD' | ./simple_shell to be run in a non-interactive mode.

Supported Control Operators

Operator	Description
;	Separates commands into command lists that can be executed unconditionally (doesn't depend on the failure or success of the previous command)
&&	Executes the next command in a command list if the previous command succeeded (had an exit code of 0)
||	Executes the next command in a command list if the previous command failed (had a non-zero exit code)

Supported Built-In Commands

1. Command: alias
   Usage: alias [name[='value'] ...]
   Description: Prints a list of aliases when no arguments are provided. If a name is provided in the arguments, it prints the alias' value in the form name='value'. If a name-value pair is provided, it creates or assigns an alias (name) with the value value. This only happens in the interactive mode.
2. Command: cd
   Usage: cd [DIRECTORY]
   Description: Changes the shell's current working directory to DIRECTORY if it is provided. If DIRECTORY is -, it switches the current working directory (PWD) with the previous working directory (OLDPWD). If DIRECTORY is not provided, the current working directory is changed to the home directory.
3. Command: env
   Usage: env
   Description: Prints the list of environment variables.
4. Command: exit
   Usage: exit status
   Description: Exits the shell with status code status (ranges from 0 to 255 inclusive) or the status code of the last command that was executed.
5. Command: help
   Usage: help
   Description: Prints the help page of a built-in command or the program.
6. Command: history
   Usage: history
   Description: Prints the list of commands that have been stored by the shell.
7. Command: setenv
   Usage: setenv VARIABLE VALUE
   Description: Sets the value of an environment variable named VARIABLE to VALUE.
8. Command: unsetenv
   Usage: unsetenv VARIABLE
   Description: Removes an environment variable named VARIABLE.

Getting Started (for contributors)

Install GCC on your system. Load the bash script into your BASH terminal using source .bashrc. This would enable the following functions to be used:

1. build - Builds the program
2. build_dbg - Creates a debugging build of the program
3. run - Runs the built version of the program
4. install - Installs the built version of the program
5. val - Launches the program with Valgrind (should be used after build_dbg)
6. viewman - Opens the man page for the program

You can find the test suite here.