In your first assignment for the Operating Systems course, you will develop a simple shell by implementing a basic REPL $($Read$,$ Eval, Print, Loop$)$ in C$.$ Your shell should support the following commands:

$1.$ cd $-$ change directory

cd

$2.$ pwd $-$ print working directory

pwd

$3.$ exit $-$ exit the shell

exit

$4.$ help $-$ display help

help

A sample output would be:

myshell$>$ help

cd $-$ change directory

pwd $-$ print working directory

exit $-$ exit the shell

help $-$ display help

mkdir $-$ create a directory

rmdir $-$ remove a directory

ls $-$ list files in a directory

cp $-$ copy a file

mv $-$ move a file

rm $-$ remove a file

$5.$ mkdir $-$ create a directory

mkdir

$6.$ rmdir $-$ remove a directory

rmdir

$7.$ ls $-$ list files in a directory

ls

A sample output would be:

myshell$>$ ls

file$1$ file$2$ file$3$

You can delimit the files with a space, or a tab $[\backslash$t$].$

$8.$ cp $-$ copy a file

cp

$9.$ mv $-$ move a file

mv

$10.$ rm $-$ remove a file

rm

Submission Guidelines

$1.$ You should submit a single zip file containing the following:

README.md $-$ a markdown file containing a brief description of your implementation, similar to a manpage

shell.c $-$ the source code for your shell

Makefile $-$ a makefile to build your shell's binary

$2.$ You should be targeting the gcc compiler, with a minimum ISO C$11$ standard. You can use the following command to ensure that your code compiles with

the correct flags and standards:

gcc $-$std$=$c$11-$pedantic shell.c $-$o shell

$3.$ Your Makefile should have the following targets:

all $-$ builds the shell

clean $-$ removes the shell binary

run $-$ runs the shell

shell.c

#include

#include

#include

void cd$($char $*$path$)$;

int main$()\{$

char input$[1024]$;

while $(1)\{$

printf$("$myshell$>")$;

fgets$($input$,1024,$ stdin$)$;

input$[$strcspn$($input$,"$

$")]=0$;

char $*$command $=$ strtok$($input$,"")$;

char $*$arg$1=$ strtok$($NULL$,"")$;

$//$ You can extend this code to support more arguments

if $($strcmp$($command$,"$cd$")==0)\{$

cd$($arg$1)$;

$\}$

$//$ You will need to extend this code to support other commands

else $\{$

printf$("$Unknown command: $\%$s

$",$ command$)$;

$\}$

$\}$

return $0$;

$\}$

void cd$($char $*$path$)\{$

$//$ Placeholder for $\text{'}$cd$\text{'}$ implementation

$\}$

$//$ The remaining functions can be implemented here