pksh

pksh is a basic shell that executes commands. It is written in C and uses C library as well as POSIX functions. It supports job control, piping, and redirection. It also supports running commands from history. Signal handling for Ctrl + C and Ctrl + Z is also present.

Compiling the code

Run make in the directory containing the shell files.

Executing the code

Run ./shell in the directory where make was just run

Cleaning up

Run make clean in the directory. This will remove the object files and the shell executable for the directory.

Description of files in the code

Each header file contains function declarations along with a small description of what the function does.

Each C file contains a function that performs a specific objective.

Thus, modularity in the code is accomplished.

We now proceed to give an overview of the files:

1. bg_terminate.c : This contains the handler that runs when a background process exits
2. exec_cd.c : This executes the cd function of the shell.
3. exec_echo.c : This executes the echo function of the shell.
4. exec_ls.c : This executes the ls function of the shell.
5. exec_pinfo.c : This executes the pinfo function that prints process information.
6. execute.c : This contains the function that either calls a function associated with a builtin, or calls launch() to launch an external process.
7. init.c : Initialises the shell.
8. launch.c : Launches the external commands, both background and foreground.
9. loop.c : Contains the Read - Eval - Print loop
10. main.c : Contains main function that intitialises the shell and calls loop()
11. Makefile : Contains rules for compiling the code.
12. parse.c : Parses string according to given delimiter.
13. prompt.c : Prints prompt for the shell
14. README.md : Contains instructions for compiling and running the code. It also contains information about the files.
15. history.c : Contains history function that prints history
16. nightswatch.c: Contains nightswatch function
17. shell.h : Contains global variables used throughout many functions
18. countargs.c : Contains function that counts the number of arguments from a list
19. exec_bg.c : Contains function that runs a stopped background process
20. exec_jobs.c : Lists jobs that are in the background that were started from shell.
21. exec_kjob.c : Function for sending a signal to a job with given job number
22. exec_setenv.c : Sets an environment variable to a given value
23. exec_unsetenv.c : Unsets value of given environment variable
24. execute_command.c : Executes the given command, either builtin or external
25. execute_pipeline.c : Executes a piped series of commands
26. linkedlist.c : Contains the implementation of the linked list used for job control
27. overkill.c : Contains function that kills all background jobs
28. quit.c : Function to exit the shell
29. recall_history.c : Implements execution of commands from history when up arrow key is pressed
30. sighandlers.c : Contains signal handlers for Ctrl + Z and Ctrl + C