SASH, A fully functional shell

Compliation, Execution

The shell executable is already provided, but if you want to rebuild it:

Inside the submitted folder, there is a makefile to create the shell executable. To create the executable type: make This creates the shell executable which can be run through ./shell

If you want to clean the object files, do : make clean This removes the obj folder and the executable

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1. Input/Output Redirection

The input and output redirection was handled in my Exec function in the utils.c file. It basically checks for any form of of redirection in the command (if any exist) and then accordingly changes the STDIN and STDOUT to the respective fd of the input/output file. After the execution of the command is over, the STDIN and STDOUT are returned to 0 and 1 respectively.

2. Command Pipelines

Pipelining is implemented in the utils.c file, in the function piping(char *), using the pipe() function. After cleaning the input command (Normalized Input) the commmand is sent to the piping() where in the the command is separated by pipes and the input/output is piped along the commands. After that each command is sent to the Exec function and there it executes the command along with any redirection.

3. I/O Redirection with Command Pipelines

The Redirection is done inside the Exec function and the piping() function sends the command to be executed to the Exec function. Since since redirection binds stronger than pipes, my code already supported the two things in one command.

4. User Defined Commands

• setenv => Implemented in the functions.c file in the Setenv function using the setenv syscall
• unsetenv => Implemented in the functions.c file in the Unsetenv function using the unsetenv syscall
• jobs => Implemented in the functions.c file in the Jobs function
• kjob => Implemented in the functions.c file in the Kjob function
• fg => Implemented in the process.c file in the Fg function
• bg => Implemented in the process.c file in the Bg function
• overkill => Implemented in the process.c file in the Overkill function
• quit => Implemented in the utils.c file and while taking input for ctrl + D

5. Signal Handling

• The two signals were handled in the main.c file in the SigTstpHandler and the SigIntHandler using the Sigaction structure.

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Bonus Features

1.Last Working Directory

Added support for cd - in the ChangeDirectory function in functions.c using a global character array which stores the just previously visited directory path.

2. Exit Codes

Added Support for Exit code reflection in the command prompt through the flag prev_stat which keeps track of the exit status of the previously executed command in the shell.