UNIX - SHELL

Files

• headers.h - contains all the required headers and functions
• shell.c - contains the main functioning of the shell managing different functions.
• display.c - displays prompt to user
• input.c - parses the input and execute the suitable command
• pwd.c - function to implement pwd command
• cd.c - function to implement cd command
• echo.c - function to implement echo command
• ls.c - function to implement ls -[la] command
• pinfo.c - function to implement pinfo command
• sys_cmd.c - fucntion to implement foreground and background processing of system commands
• history.c - functions to implement the history command
• piping.c - handles piping
• redirection.c - handles redirections
• setenv.c - sentenv command to set environment variable
• unsetenv.c - unsetenv command to unset environment variable
• jobs.c - job command to list active jobs
• kjob.c - kjob command to kill a job
• fg.c - fg command to bring background process to foreground
• bg.c - bg command to run stopped background process
• overkill.c - overkill command to kill all background processes
• signal_control.c - Signal Handeling
• utility.c - contains all the utility functions

Fuctioning

• cd - 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 to the terminal
• ls -[al] - lists all files of the given directory(s) with respcet to mentioned flags
• 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.
• history [n] - Prints history of n (max 20) commands. Default n = 10.
• setenv - creates/changes the environment variable "var" and sets its value to "value"
• unsetenv var - unsets the value of the environment variable "var"
• jobs - prints a list of all currently running jobs along with their job ids , pid, in particular, background jobs, in order of their creation along with their state – Running or Stopped.
• ​kjob - takes the job id of a running job and sends a signal value to that process
• ​fg ​- brings a running or a stopped background job with given job number to foreground
• ​bg ​- changes a stopped background job to a running background
• ​overkill - kills all background process at once
• quit/q/exit - exits the shell
• CTRL-Z - changes the status of currently running job to stop, and push it to background. If there is no foreground job, then the signal has no effect.
• CTRL-C - causes a SIGINT signal to be sent to the current foreground job of the shell​. If there is no foreground job, then the signal has no effect.
• CTRL-D - exits the shell
• Any process can be run to Background by adding '&' in the command.
• cd can handle [~ . .. -] special symbols.
• $'cd -' takes user to last working directory.
• ls can handle [~ . ..] special symbols.

How to run :-

foo@bar:~$ make
foo@bar:~$ ./shell