hy345sh — Custom Unix Shell

A lightweight Unix shell written in C, built from scratch as a systems programming exercise. It supports command execution, I/O redirection, sequential commands separated by semicolons, and single-pipe piping between two commands.

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Features

• Interactive prompt showing the current working directory
• Command execution via execvp with full argument support
• Built-in chdir for directory navigation
• Built-in quit to exit the shell
• I/O redirection — < for stdin, > for stdout
• Sequential commands separated by ;
• Single pipe (|) between two commands

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Build

gcc -Wall -O2 -o hy345sh hy345sh.c

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Run

./hy345sh

You will be greeted with a prompt like:

<4581>-hy345sh@sfyrixtras:/home/user $

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Usage Examples

Basic command

<4581>-hy345sh@sfyrixtras:~ $ ls -la

Output redirection

<4581>-hy345sh@sfyrixtras:~ $ ls > output.txt

Input redirection

<4581>-hy345sh@sfyrixtras:~ $ sort < input.txt

Sequential commands

<4581>-hy345sh@sfyrixtras:~ $ ls ; pwd ; echo hello

Pipe

<4581>-hy345sh@sfyrixtras:~ $ ls | grep .c

Change directory

<4581>-hy345sh@sfyrixtras:~ $ chdir /tmp

Exit

<4581>-hy345sh@sfyrixtras:~ $ quit

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Limitations

• Pipes support only a single | (two-command pipeline)
• No background process support (&)
• No environment variable expansion
• No command history

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File Structure

hy345sh/
└── hy345sh.c       # Full shell implementation

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Author

Stylianos Athanasiou — CSD4581