Project 4 - Simple Bash

Bash

The Bash is a command processor that runs in most Linux distributions. It is the default login shell of Ubuntu and Solaris. This command processor can parse the commands that user type in the text window and execute them. Except running in text window, Bash can also parse shell script which contains commands in a file. In this project, we are going to implement a simple Bash in C.

Requirement

The input of your implemented simple bash will be a shell script by redirection (such as shell test.sh) or by manual input. The simple bash needs to behave the same as bash in Ubuntu. We will check your implementation by manual input and by redirecting your output to a text file (such as shell test.sh > output.txt). Therefore, you need to pay attention to different output formats. For example, try typping ls in text window and ls > output.txt.

The following functions are likely to be helpful: fork, exec, execvp, wait, waitpid, kill, dup, pipe, strncmp, strlen, malloc, free, getcwd, chdir , open, close, readline, gets, fgets, getchar, signal, getpwuid, gethostname (NO system!!!)

You are going to implement following stuff:

• The prompt which you should indicate the login name, host name and current directory is required for manual input, such as yang@yang-XPS-13-9350:~/CA$
• Relative or absolute pathnames are allowed to use, such as sh and /bin/sh
• Redirection including <, >, >> is required.
• Background command which puts an & in the end of command is required.
• Built-in command which no new process is created but instead the functionality is built in the shell needs to be implement including cd, jobs, exit, kill. kill %num means terminate the process numbered %num returned by jobs. You do not need to implement cd -.
• Pipe | which send the STDOUT of the previous command to the STDIN of the next command is required. There might be multiple | in the command. STDERR is not required.
• Each item in the command string is seperated at least one space.
• All the test cases are legal inputs. No escape sequence. No quotation.

Submission and Grading

We will be using git for this project as well. Refer to previous Git Usage Guide for basic git usage. Create your team's git repo for Project 4 on GitHub, initialize your framework directory as a git repository (which means it directly contains shell.c, parse.c, parse.h, Makefile), and push your work onto your remote repository. Submit your work to Autolab with an archive project4.tar, which is created through:

The structure of your git repository should be the same as below, where parse.c and parse.h contain the code for parsing the command, shell.c contains the code for executing the command. The Makefile should produce an executable file shell for evaluation.

We will compare the behavior of your shell with bash under Ubuntu 16.04. We will test the output of your shell using redirection.