In this I implemented POSIX Shell using cpp

• make clean
• make
• make run

• echo
• cd
• pwd
• ls
• history
• foreground and background
• pinfo
• search
• pipeline

• In echo only "---" string is printed
• In cd ~ is treated as home path
• In pwd starting path is treated as home path
• In history only 20 recent commands is shown
• In pipeline all commands are executed using execvp