RUNNING:
Run "make"
Execute by using "./shell"
Type "exit" to exit the shell

FEATURES:
Shell prompt:
A shell prompt similar to the original shell appears.The directory from which the shell has been invoked
will be the home directory and corresponding changes in the directory like cd are reflected as well.

Built-in commands:
Some built-in commands like cd,pwd and echo have been implemented.
  cd command:
    "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

  pwd command:
    "pwd" - prints path of present working directory
          - prints absolute path for the directories previous to the one from which shell has been invoked, and path relatuve to this directory from there on.

  echo command:
    "echo" - prints empty line.
    "echo text" - prints "text"

Ls command:
  ls takes arguments as flags (in the form -(flagname)) and directories (in the form -(directory name)) 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 -a" - display hidden files
  "ls -l" - long list
  "ls -al"/"ls -la"/"ls -l -a"/"ls -a -l" - long list including hidden files

Pinfo command:
It prints the process related info.
    "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)


Foreground and background processes:
Executing a command in the foreground implies that your shell will wait for this process to complete and regain control when
this process exits.
Any command invoked with "&" is treated as background command. This implies that your shell will spawn that process and doesn't wait for
the process to exit. It will keep taking user commands.

If the background process exits then the shell must display the appropriate
message to the user.

Input-output redirection functionality:
Output of a command can be redirected to another file or input can be drawn from a file.Appropriate error
handling is also done(like displaying appropriate error message if file does not exist for input,creating an Output
file with 644 permissions,etc)
  Command format :
    "command1" > "file1" < "file2"
    "command1" >> "file1" < "file2"

Command redirection using pipes:
Support is provided to any number of pipes.(Output of one command is taken as input to the next command seperated using 
pipes )
  Command format :
    "command1" | "command2"

I/O redirection + pipes redirection:
Pipes redirection including i/o redirection can be done.
  Commans format:
    "command1" < "file1" | "command2" > "file2"

User defined commands:
  Set environmental variable.
    "setenv var [value]" - sets var to value if given else to empty string
    "getenv var" - prints the value of the environmental variable var if it exits else error
    "unsetenv var" - destroys the environmental variable var of exists else error
    "jobs" - Prints a list of all currently running background jobs along with their pid in the order
    of their creation along with their states.
    "kjob <jobNumber> <signalNumber>" - Takes the jobNumber and sends the given signal value to that
    process
    "fg <jobNumber>" -  Brings a running or a stopped background job with given job
number to foreground
    "bg <jobNumber>" - changes a stopped background job to a running background
job.
    "overkill" - kills all background process at once.
    "quit" - exits the shell.
    "CTRL-Z" - It should change the status of currently running job to stop, and push it
in background process.
"CTRL-C" -  It should cause a SIGINT signal to be sent to the current foreground
job of your shell. If there is no foreground job, then the signal should not have
any effect.






Bonus:
Personal reminder
  "remindme time statement" - prints "statement" after "time" seconds.

Clock commmand
  "clock -t time -n duration" - prints date and time after every "time" seconds for n seconds.

Files and their corresponding parts:
builtIn.c - checks if the command is builtin and executes if True
getInput.c - takes input from prompt and divides into different commands and arguments for each
ls.c - checks if the command is ls and executes it
pinfo.c - checks if the command is pinfo and executes it
remindme.c - checks if the command is remindme and executes it
clock.c - checks if the command is clock and executes it
convertCWD.c - gets the current working directory's absolute path and converts it as mentioned in shell prompt.
redirection.c - checks if there is any redirection part and sets the required values and also handle piping.
userdef.c - does all the userdefined commands part