description.txt

Description of the shell: 

Internal commands -- cd, pwd, echo, exit
cd options: cd "dir_name"
            cd -L "dir_name"
            cd -P "dir_name"
            cd --help

pwd options: pwd
             pwd -L
             pwd -P
             pwd --help

echo options: echo "string"
              echo -n "string"
              echo -E "string"

exit: To eit the command line or shell

External commands -- mkdir, rm, date, cat, ls
mkdir options: mkdir "folder name"
               mkdir -v "folder name"
               mkdir --version

rm options: rm "file name"
            rm -v "file name"
            rm -d "directory name"

date options: date
              date -U
              date -R 

cat options: cat "filename"
             cat -E "filename"
             cat -T "filename"

ls options: ls
            ls -a
            ls -m
            ls --version

These all commands are handled with fork, wait and execvp
If we &t is written and then these commands are executed then
they will be executed by pthread_create, system, pthread_join

All the corner cases are handled and program is running succesfully
             

Assumption: I assumed that the present working directory is not to be shown everytime. I just showed @> everytime in the shell.
            we can get present working directory by pwd command.


Corner cases:
1. If the user enter nothing there will be continuation
2. If user enters the command which is not present in Description, shell will show Invalid Input.
3. If the user enters the wrong option of the command it shows Invalid Input -- option
4. If the user enters wrong or invalid directory it shows Error : No such file or directory


Test case:
// Internal commands
cd ..
pwd
cd -P assignment1
pwd

cd --help
pwd -L
pwd -p
pwd --help
cd -L assignment1

echo
echo hello
echo -n hello
echo -E hello

// same with pthreads
&t cd ..
&t pwd
&t cd assignment1
&t pwd

&t cd --help
&t pwd -L
&t pwd -p
&t pwd --help
&t cd -L assignment1

&t echo
&t echo hello
&t echo -n hello
&t echo -E hello

exit

// External commands
date 
date -U 
date -R 

ls 
ls -a
ls -m
ls --version

cat cat.c
cat -E cat.c
cat -T cat.c

mkdir hello
rm -d hello
mkdir -v hello
rm -d hello
mkdir --version 

// new.txt and new1.txt will be created
rm -v new.txt 
rm new1.txt

exit

// with pthreading

&t date 
&t date -U 
&t date -R 

&t ls 
&t ls -a
&t ls -m
&t ls --version

exit

&t cat cat.c
&t cat -E cat.c
&t cat -T cat.c

&t mkdir hello
&t rm -d hello
&t mkdir -v hello
&t rm -d hello
&t mkdir --version 

exit

// new.txt and new1.txt will be created
&t rm -v new.txt 
&t rm new1.txt

exit