CShell: An implementantion of the terminal using system calls in the C language.
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Vijayraj Shanmugaraj
20171026

USAGE
- run "make"
- execute by using "./csh"
- type "quit" to exit the shell

FEATURES

ls command (file: ls.c)
Usage:
- ls takes arguments as flags (-l, -a) and directories in any order.
- It lists the files of all the directories mentioned, in the form of option selected by the flags.
- If there is no directory mentioned, it lists the files of current directory

* "ls" - lists in alphabetical order
* "ls -a" - display hidden files
* "ls -l" - long list
* "ls -al"/"ls -la"/"ls -l -a"/"ls -a -l" - long list including hidden files

cd command (file: cd.c)
* "cd (absolute path)" - goes to absolute path
* "cd" - goes to ~/
* "cd ~/(pathname)" - goes to ~/(pathname)
* "cd .." - goes to previous directory
* "cd ." - goes to same directory

echo command (file: echo.c)
* "echo" - prints empty line
* "echo text" - prints "text"
* "echo 'text' " - prints "text"
* "echo $var" - prints value of linux environment variable "var"

pwd command (file: pwd.c)
* "pwd" - prints absolute path of present working directory

pinfo command (file: pinfo.c)
* "pinfo" : prints the process related info of the shell program
* "pinfo <pid>" : prints the process info about given pid
- pid --
- Process status -- {R/S/S+/Z}
- Memory
- Executable path -- (Absolute path - includes ~/ if executable is present inside the shell directory)

clock command: (file: clock.c)
* prints utc time and date for given duration between given intervals
* Usage: clock -t [interval] -n [duration]

remindme command: (file: remindme.c)
* reminds you with your custom message after the given number of seconds elapse
* shell can take in commands during this time

setenv command: (file: setenv.c)
*If environment variable var does not exist, then the shell creates it.
*The shell will set the value of var to value, or to the empty string if value is omitted.
*Can set the value of existing environment variable too

unsetenv command: (file: setenv.c)
*Shell destroys the environment variable var

jobs command: (file: exec_new.c)
*Prints a list of all currently running jobs along with their pid, in particular, background jobs, in order of their creation along with their state

kjob command: (file: exec_new.c)
*Takes the job id of a running job and sends a signal value to that process

fg command: (file: exec_new.c)
*Brings a running or a stopped background job with given job number to foreground.

bg command: (file: exec_new.c)
*Changes a stopped background job to a running background job

overkill command: (file: exec_new.c)
*Kills all background process at once.

{exec.c takes care of running foreground and background processes, and printing appropriate message to user when a background process ends}
{Redirection, piping and a combination of both are supported. For redirection, use spaces between redirection arrows (<,>,>>)}
{Signal handling has been taken care of. ^C, ^Z do not affect the shell, but only the foreground process(if any) running on the shell}