Simple Shell (HSH)

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Overview

HSH is a simple Unix-like shell implemented in C, inspired by the classic Thompson Shell. It aims to provide core shell functionalities while helping users understand how shells work internally.

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Features

• Interactive Prompt: Displays a prompt (#cisfun$) and waits for user input.
• Command Execution: Supports running executables with arguments.
• Error Handling: Prints informative error messages when commands fail or cannot be found.
• EOF Handling: Properly handles the End-of-File (Ctrl+D) input to exit gracefully.
• PATH Support: Searches executable paths based on the PATH environment variable.
• Signal Handling: Captures Ctrl-C (SIGINT) to avoid shell termination.
• Command Separators: Supports command chaining using ;.
• Logical Operators: Handles && and || for conditional command execution.
• Variable Replacement: Expands special variables like $? (last exit status) and $$ (process ID).
• Comments: Supports inline comments starting with #.
• File Input: Can execute commands from a file input.

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Built-in Commands

Command	Description
exit [n]	Exit the shell, optionally specifying an exit status n.
env	Print the current environment variables.
setenv [var] [val]	Set or update an environment variable.
unsetenv [var]	Remove an environment variable.
cd [dir]	Change the current working directory.
help [builtin]	Display documentation about built-in commands.

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Installation

1. Clone the repository:

   git clone https://github.com/godfreydekew/simple_shell.git
   cd simple_shell

2. Compile the project:

   make

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Usage

Run the shell by executing:

./bin/myshell

You will see the prompt:

#cisfun$

Now you can enter commands just like in a standard shell:

Example Session

#cisfun$ /bin/ls -l /etc
total 12
-rw-r--r-- 1 root root 1234 Jul 25 10:00 hosts
-rw-r--r-- 1 root root 4321 Jul 24 15:00 passwd
#cisfun$ cd /usr/local
#cisfun$ pwd
/usr/local
#cisfun$ setenv GREETING HelloShell
#cisfun$ echo $GREETING
HelloShell
#cisfun$ unsetenv GREETING
#cisfun$ env
PATH=/usr/local/bin:/usr/bin:/bin
HOME=/home/user
...
#cisfun$ exit 0

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Clean up

make clean