c++ create a A readevalprint loop hat takes single user inputs (i.e. single expressions), evaluates them, and returns the result to the user. You are NOT allowed to use fork, execve(2) (or the exec(3) family of functions), system(3), popen(3), and pclose(3)

Here are some examples (first line is a repl$ prompt that your program will literally print to standard output plus user input that your program will read in from the user; subsequent lines are output):

repl$ cat file.txt

 Job STDIN = STDIN_FILENO Job STDOUT = STDOUT_FILENO Job STDERR = STDERR_FILENO 

 0 pipe(s) 1 process(es) 

 Process 0 argv: 0: cat 1: file.txt 

repl$ cat file.txt | less

 Job STDIN = STDIN_FILENO Job STDOUT = STDOUT_FILENO Job STDERR = STDERR_FILENO 

 1 pipe(s) 2 process(es) 

 Process 0 argv: 0: cat 1: file.txt 

 Process 1 argv: 0: less 

repl$ cat file.txt | grep // > out.txt

 Job STDIN = STDIN_FILENO Job STDOUT = out.txt (truncate) Job STDERR = STDERR_FILENO 

 1 pipe(s) 2 process(es) 

 Process 0 argv: 0: cat 1: file.txt 

 Process 1 argv: 0: grep 1: // 

repl$ cat | grep // | less < in.txt >> out.txt

 Job STDIN = in.txt Job STDOUT = out.txt (append) Job STDERR = STDERR_FILENO 

 2 pipe(s) 3 process(es) 

 Process 0 argv: 0: cat 

 Process 1 argv: 0: grep 1: // 

 Process 2 argv: 0: less 

repl$ cat f1.txt f2.txt > out.txt e>> log.txt

Job STDIN = STDIN_FILENO

Job STDOUT = out.txt (truncate)

Job STDERR = log.txt (append) 

0 pipe(s) 1 process(es) 

Process 0 argv: 0: cat 1: f1.txt 2: f2.txt 

repl$ echo "my \"cool\" shell" | less 

Job STDIN = STDIN_FILENO Job STDOUT = STDOUT_FILENO Job STDERR = STDERR_FILENO 

1 pipe(s) 2 process(es) 

Process 0 argv: 0: echo 1: my "cool" shell 

Process 1 argv: 0: less 

repl$ cat file1 file2 file3

Job STDIN = STDIN_FILENO Job STDOUT = STDOUT_FILENO Job STDERR = STDERR_FILENO 

0 pipe(s) 1 process(es) 

Process 0 argv: 0: cat 1: file1 2: file2 3: file3 

" | " distinguishes pipe " < " Job STDIN " > " Job STDOUT and if there is an 'e' infront of < or > Job STDERR