Psush - A Custom Linux Shell

Psush is a custom Linux shell. This shell replicates core functionalities of standard shells while adding custom features to enhance user interaction. Written in C, Psush focuses on efficiency, modularity, and error-free execution.

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Features

Built-in Commands

• bye: Exit the shell.
• cd: Change directory (cd <dir> or cd to switch to the home directory).
• cwd: Display the current working directory.
• history: Show the last 15 commands entered.
• echo: Echo the arguments passed, without variable expansion.

External Commands

• Executes any external Linux command (e.g., ls, cat, grep) with full support for command-line options and arguments.

Additional Functionalities

• Pipelines: Support for piped commands (e.g., ls | wc).
• Input/Output Redirection:
  • Redirect input (wc < file.txt).
  • Redirect output (ls > output.txt).
• Custom Prompt: Dynamically displays the current working directory, user name, and system name.
• Signal Handling: Graceful handling of Ctrl+C (SIGINT) without terminating the shell.
• Memory Management: No memory leaks, validated using valgrind.
• No Orphans/Zombies: Proper process handling to avoid orphaned or zombie processes.

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How to Build

A Makefile is provided for streamlined building and cleaning.

Build the Shell

make

Clean Up Compiled Files

make clean

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How to Run

Run PSUsh from the terminal:

./psush

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Requirements

• Development Environment: Linux
• Compiler: GCC with the following flags:
  • -g -Wall -Wshadow -Wunreachable-code -Wredundant-decls
  • -Wmissing-declarations -Wold-style-definition
  • -Wmissing-prototypes -Wdeclaration-after-statement
  • -Wno-return-local-addr -Wuninitialized -Wextra -Wunused
• Language: C

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Design Highlights

• Command Parsing: Uses linked lists to handle pipelines and arguments.
• Dynamic Prompt: Displays user and system-specific details.
• Error Handling: Custom messages for failed commands and memory errors.
• Code Structure: Modular design with reusable components in cmd_parse.c and cmd_parse.h.