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Milestone 2

Memory leaks and undefined behaviors are not tested in the milestone.

All of the test cases are very basic input, and we'll give hints on many common errors. You'll get -50% deduction of a certain (sub)task if you get a wrong answer in any of its cases.

Tasks

6. Pipes: [5+5+5+10]

6.1 Basic pipe support (e.g. echo 123 | grep 1); [5]

• Case: 1-2

6.2 Run all ‘stages’ of piped process in parallel. (e.g. yes ve482 | grep 482); [5]

• Case: 3-4
• Your shell is likely to get TLE (Time Limit Exceeded) if not running in parallel.

6.3 Extend 6.2 to support requirements 4. and 5. (e.g. cat < 1.txt 2.txt | grep 1 > 3.txt); [5]

• Case: 5-6
• Input redirection can only be found in the first command, and output redirection can only be found in the last command.

6.4. Extend 6.3 to support arbitrarily deep “cascade pipes” (e.g. echo 123 | grep 1 | grep 1 | grep 1) [10]

• Case: 7-8

7. Support CTRL-D (similar to bash, when there is no/an unfinished command); [5]

• Case: 9-10
• Don't forget to print "exit" when exiting your shell

8. Internal commands: [5+5+5]

8.1. Implement pwd as a built-in command; [5]

• Case: 11

8.2 Allow changing working directory using cd; [5]

• Case: 12

8.3. Allow pwd to be piped or redirected as specified in requirement 4.; [5]

• Case: 13-14
• eg. pwd | cat > 1.txt

9. Support CTRL-C: [5+3+2+10]

• Your shell is likely to get TLE (Time Limit Exceeded) if CTRL-C is not handled correctly.
• You should NOT use the kill syscall, especially kill(0, signal), it may destroy the judger. You will be sent to the honor council if you intentionally use it.

9.1. Properly handle CTRL-C in the case of requirement 4.; [5]

• Case: 15

9.2. Extend 9.1 to support subtasks 6.1 to 6.3; [3]

• Case: 16

9.3. Extend 9.2 to support requirement 7., especially on an incomplete input; [2]

• Case: 17

9.4. Extend 9.3 to support requirement 6.; [10]

• Case: 18