lsh (laaaad's Shell)

Pre-requisites

You need to install ncurses.h library to make this work. You can install it by using

• sudo apt-get install libncurses5-dev libncursesw5-dev

Usage

1. make
2. ./lsh

To delete all .o files, run make clean.

Files

* main.c        - contains the main functioning of the shell
* def.h         - contains all the required headers and functions
* prompt.c      - to display the prompt to user
* cd.c          - cd command
* pinfo.c       - pinfo command
* echo.c        - echo command
* pwd.c         - pwd command
* ls.c          - ls command
* fg_bg.c       - handling background and foreground processes for commands which are executed through execvp
* history.c     - history command
* nightswatch.c - nightswatch command
* cronjob.c     - cronjob command
* execute.c     - helper file which executes the commands
* bg.c          - bg command
* fg.c          - fg command
* env.c         - setenv and unsetenv commands
* jobs.c        - jobs command
* redirection.c - helper file for executing input and output redirection
* upArrow.c     - up arrow functionality

Functioning

* cd <directory path>                       - Changes directory to the given path. Changes to shell home if no directory is provided
* pwd                                       - Shows the absolute path of the current working directory 
* echo                                      - Prints the message to the terminal. Handled single and double quotes.
* ls [al] <directory path>                  - Handles all variations of ls with a and l flags and directory path
* pinfo [pid]                               - Prints process related info (pid, Process Status {R, S, S+, Z}, memory and Executable Path) about given pid. Prints process related info of shell program if no pid is provided
* exit                                      - Exits the shell
* quit                                      - Similar to exit
* history [n]                               - Prints history of n (max 20) commands. Prints history of maximum 10 commands if n is not provided
* nightswatch -n [time] <type>              - Repeats command of type <type> every <time> seconds until 'q' is pressed.
* setenv var [value]                        - sets the value of the environment variable specified by var (create if it does not exist) to [value].
* unsetenv var                              - destroys the environment variable specified by var
* jobs                                      - prints list of all currently running background jobs along with their pid and their current state
* kjob <jobNumber> <signalNumber>           - takes the job id of a running job and sends a signal value to that process
* fg <jobNumber>                            - brings a running or a stopped background job with a given job number to background
* bg <jobNumber>                            - changes a stopped background job to a running background job
* overkill                                  - kills all background process at once
* CTRL-Z                                    - changes the status of currently running job to stop, and pushes it in background process
* CTRL-C                                    - cause a SIGINT signal to be sent to the current foreground job of this shell.
* 'UP' arrow key                            - kth previous command gets executed on pressing the 'UP' arrow key k times
* cronjob                                   - executes a particular command in fixed time interval for a certain period
* input-output redirection functionality    - replicates (almost) what bash does
* piping functionality                      - replicates (almost) what bash does
* All other commands are implemented using execvp. 
* Background Processing (can be run with '&') is handled for commands executed through execvp