qureshinomaan / Shell

An implementation of Bash in C.

Shell

This is a Shell developed entirely in C. The shell emulates the normal bash in linux systems. It is able to handle bakground processes, foreground processes, input-output redirection, command redirection etc.

Installing

A step by step series of examples that tell you how to get a development env running

Copy an paste on your terminal the set of commands below.

git clone https://github.com/qureshinomaan/Shell.git

make 

./shell

Features

Display

• The format is <username@system_name:curr_dir>
• ~ signifies the address of Home Directory.

Commands

pwd

• Prints the path present working directory.

cd

• cd changes the pwd to the specified directory path.

ls [al]

• lists all the file in the pwd.

pinfo

• Prints the process related info of Shell program.

pinfo

• prints the process info about given pid.

history

• Tells the last 10 commands executed on shell.

history

• Prints the last 'n' commands.
• 'n' is specified by user.

All Other General shell commands.

• All other commands like cat, grep, etc. can be executed through the shell.
• The difference is that they are builtin and ls, pwd, cd were built by me.

setenv var [value] :

• If the enviroment variable does not exist, then creates it.
• Modifies the existing value if the environment variable already exists.

unsetenv var

• Destroys the evironment variable if exists.

jobs

• prints all the currently running jobs along with their pids.

kjob

• Takes the job number of the process and sends the signal specified by signalNumber to it.

fg

• Brings the job running in background to the foreground.

bg

• Changes a stopped background job to a running background job.

overkill

• Kills all background process at once.

quit

• Exits the shell.

CTRL-Z

• Changes teh currently running job to stop, and pushes it to background process.

CTRL-C

• Sends a SIGINT signal to the current forground job of this shell.
• If there is no foreground process currently this should have no effect.

Foreground Processes

• Just type the command's name you want to run.
• These processes have the access of input and output on the terminal window.
• Example

vim bello;ls;

Background Processes

• Type the command's name you want to execute. End it with a &.
• These processes run in the background meaning they do not have input and output accesses from the terminal window.
• Example

vim bello &

Input/Output Redirection.

• Input Redirection

sort < lines.txt

• Output Redirection

cat bello.txt > hello.txt  //Overwriting hello.txt
cat bello.txt >> hello.txt  //Appending to hello.txt

• Input-Output Redirection

sort < lines.txt > output.txt 

Command Redirection Using Pipes

• A pipe is a basically a channel of communication between two processes.
• Identified by '|'
• Example

cat bello.txt | grep hello
ls | grep *.txt > out.txt 

Contributing

Please read CONTRIBUTING.md for details on our code of conduct, and the process for submitting pull requests to us.

Authors

• Nomaan Qureshi - Initial work

Acknowledgments

• CSE-1 Course TA's.
• Professor P.K. Reddy, IIIT Hyderabad.