Overview

As the name suggests, the goal is creating a simple shell that implements the most essential features of a shell.

Description

• This project is implemented in c and is compilable with a Makefile.
• Memory leaks free, Memory leaks are not to be tolerated.
• Error free, an error displayed in case something went wrong.
• This shell is based on bash behavior.
• The final program Displays a prompt when waiting for a new command with a command history.
• The program searches and launches the right executable (based on the PATH environment variable or using a relative or an absolute path).
• The program uses only one global variable for signal handling.
• The program has ’ (single quote) processing, which should prevent the shell from interpreting the meta-characters in the quoted sequence.
• It also has " (double quote) processing which should prevent the shell from interpreting the meta-characters in the quoted sequence except for $(dollar sign).
• The shell implements redirections: < > >> and <<.
• The shell also implements pipes |, The output of each command in the pipeline is connected to the input of the next command via a pipe.
• The shell expands environment variables to their values ($ followed by a sequence of characters).
• The shell expands $? to the exit status of the most recently executed foreground pipeline.
• The shell handles the following signals: ctrl-C, ctrl-D and ctrl-\.
• The shell implements the following built-ins:
  • echo with option -n.
  • cd with only a relative or absolute path.
  • pwd with no options.
  • export with no options.
  • unset with no options.
  • env with no options or arguments.
  • exit with no options.

New Concepts

• Advanced memory management
• Advanced error handling
• Debugging multiprocess code
• Shell Prompt
• Command Parsing
• Command Execution Model
• Process Creation and Control (fork, exec, wait, waitpid...)
• Redirection and File Descriptors
• Pipes
• Environment Variables
• Built-in Commands
• Job Control
• Signal Handling