simpsh

About implemenation
If any invalid options are typed, the program skips over the command.
However, if that is a file option, it also skips the file descriptor position of that invalid command, so that the later command works as intended.
so, if you type (in the folder with in.txt out.txt err.txt, but no dne.txt)
--rdonly in.txt --wronly dne.txt --wronly out.txt --wronly err.txt \
--command 0 1 2 cat \
--command 0 2 3 cat
Since the wronly assigment of dne.txt (at fd positon 1) is skipped and 1 becomes invalid, the first command gets skipped over, but the second command works just as intended (get the input from in.txt, output to out.txt, error to err.txt)

Also, I have specified the command option so that three file desriptors passed in must be a different ones. If one of them is same as the other, the command is looked to be invalid and therefore is skipped.

--Profile option shows the user/system time the parent process used between each option after the --profile option (this does NOT include profile option itself). Then, after all is done, it shows parent/child user/system time (this value is equivalent to using times option in bash/dash).
 

Test Cases
I checked the basics with the test cases, since more advanced testing was done on TA's script.
Test case 1 tests if normal in/out works
Test 2 tests if program returns 1 when rdonly file does not exist
Test 3 tests if program retuns 1 when wronly file does not exist
Test 4 tests if commands with reguired arguments are marked as invalid if there is no argument (e.g. no file name for --rdonly)
Test 5 tests if rdwr works
Test 6 tests if pipe works
Test 7 tests if abort works

Limitations
I closed all fds and freed the allocated memory for both PID and File Descriptors, but I wasn't sure how to close the file when signal handler was called, because signal handler function can only take 1 argument (that is, the signal number) and therefore cannot pass the pointer of PID array / FD array