Network Programming Project 1 - NPShell

Deadline: Monday, 2019/10/21 23:59

HW1

Introduction

In this project, you are asked to design a shell with special piping mechanisms.

Scenario of using npshell

• Some important settings
  1. The structure of the working directory working_dir ├─ bin │ ├─ cat │ ├─ ls │ ├─ noop │ ├─ number │ ├─ removetag │ └─ removetag0 └─ test.html
  • The directory contains executables
  • A program that does nothing
  • Add a number to each line of input
  • Remove HTML tags and output to STDOUT
  • Same as removetag, but outputs error messages to STDERR.
  2. In addition to the above executables, the following are built-in commands supported by your npshell
  • setenv
  • printenv
  • exit
• Scenario bash$ ./npshell // execute your npshell % printenv PATH // initial PATH is bin/ and ./ bin:. % setenv PATH bin // set PATH to bin/ only % printenv PATH bin % ls bin test.html % ls bin cat ls noop number removetag removetag0 % cat test.html > test1.txt % cat test1.txt <!test.html> <TITLE>Test</TITLE> This is a test program for ras. % removetag test.html Test This is a test program for ras. % removetag test.html > test2.txt % cat test2.txt Test This is a test program for ras. % removetag0 test.html Error: illegal tag "!test.html" Test This is a test program for ras. % removetag0 test.html > test2.txt Error: illegal tag "!test.html" % cat test2.txt Test This is a test program for ras. % removetag test.html | number 1 2 Test 3 This is a test program 4 for ras. 5 % removetag test.html |1 // this pipe will pipe STDOUT to next command % number // the command's STDIN is from previous pipe 1 2 Test 3 This is a test program 4 for ras. 5 % removetag test.html |2 ls // |2 will skip 1 command and then pipe bin test1.txt // STDOUT to the next command test.html test2.txt % number // the command's STDIN is from the 1 // previous pipe (removetag) 2 Test 3 This is a test program 4 for ras. 5 % removetag test.html |2 // pipe STDOUT to the next next command % removetag test.html |1 // pipe STDOUT to the next command (merge with the previous one) % number // STDIN is from the previous pipe 1 2 Test 3 This is a test program 4 for ras. 5 6 7 Test 8 This is a test program 9 for ras. 10 % removetag test.html |2 removetag test.html |1 % number |1 number 1 1 2 2 Test 3 3 This is a test program 4 4 for ras. 5 5 6 6 7 7 Test 8 8 This is a test program 9 9 for ras. 10 10 % removetag test.html | number |1 number 1 1 2 2 Test 3 3 This is a test program 4 4 for ras. 5 5 % ls |2 ls bin test1.txt test.html test2.txt % number > test3.txt % cat test3.txt 1 bin 2 test.html 3 test1.txt 4 test2.txt % removetag0 test.html |1 Error: illegal tag "!test.html" // output error message to STDERR % number 1 2 Test 3 This is a test program 4 for ras. 5 % removetag0 test.html !1 // this pipe will pipe both STDIN and STDERR // to the next command % number 1 Error: illegal tag "!test.html" 2 3 Test 4 This is a test program 5 for ras. 6 % date Unknown command: [date]. // TA manually move the executable, date, into ${working_dir}/bin/ % date Sun Sep 8 22:47:02 CST 2019 % exit bash$

Requirements and Hints

• In this project, the commands noop , number , removetag , removetag0 are offered by TA. Please download them from E3, compile them and put these executables into the folder ${working_dir}/bin/. e.g., g++ noop.cpp -o ${working_dir}/bin/noop
• ls and cat are usually placed in the folder /bin/ in UNIX-like systems. Please copy them into the folder ${working_dir}/bin/ e.g., cp /bin/ls /bin/cat working_dir/bin/
• During demo, TA will copy additional commands to bin/, which is under your working directory. Your npshell program should be able to execute them.
• You must use exec-based functions to run commands, except for built-in commands ( setenv , printenv and exit ). You must not use functions like system() or some other functions to do the job.
• When you implement output redirection (>) to a file, if the file already exists, the file should be overwritten. (not append)
• You don't have to worry about outputting to both file and pipe for the same command. % ls > test.txt | cat # this will not appear
• You don't have to implement input redirection from a file (<)
• You can only implement the npshell with C and C++, other third-party libraries are NOT allowed .

Specification

• Input
  1. The length of a single-line input will not exceed 15000 characters.
  2. Each command will not exceed 256 characters.
  3. There must be one or more spaces between commands and symbols (or arguments), but no spaces between pipe and numbers. % cat hello.txt | number % cat hello.txt |4 % cat hello.txt !4
  4. There won’t exist any '/' character in test cases.
• NPShell Behavior
  1. Use "% " as the command line prompt. Notice that there is one space character after % .
  2. The npshell terminates after receiving the exit command or EOF .
  3. Notice that you must handle the forked processes properly, or there might be zombie processes.
  4. Built-in commands ( setenv , printenv , exit ) will appear solely in a line. No command will be piped together with built-in commands.
• setenv and printenv
  1. The initial environment variable PATH should be set to bin/ and ./ by default. % printenv PATH bin:.
  2. setenv usage: setenv [variable name] [value to assign]
  3. printenv usage: printenv [variable name] % printenv QQ # Show nothing if the variable does not exist. % printenv LANG en_US.UTF-8
  4. The number of arguments for setenv and printenv will be correct in all test cases.
• Numbered-Pipes and Ordinary Pipe
  1. |N means the STDOUT of the left hand side command should be piped to the next N -th command, where 1 ≤ N ≤ 1000.
  2. !N means both STDOUT and STDERR of the left hand side command should be piped to the next N -th command, where 1 ≤ N ≤ 1000.
  3. | is an ordinary pipe, it means the STDOUT of the left hand side command will be piped to the right hand side command. It will only appear between two commands , not at the beginning or at the end of the line.
  4. The command number still counts for unknown command. % ls |2 ctt Unknown command: [ctt]. % number 1 bin/ 2 test.html
  5. setenv and printenv count as one command. % ls |2 % printenv PATH bin:. % cat bin test.html
  6. Empty line does not count. % ls |1 % # press Enter % number 1 bin/ 2 test.html
• Unknown Command
  1. If there is an unknown command, print error message as the following format: Unknown command: [command]. e.g. % ctt Unknown command: [ctt].
  2. You don't have to print out the arguments. % ctt -n Unknown command: [ctt].
  3. The commands after unknown commands will still be executed. % ctt | ls Unknown command: [ctt]. bin/ test.html
  4. Messages piped to unknown commands will disappear. % ls | ctt Unknown command: [ctt].

Submission

1. Create a directory named as your student ID , put all files into the directory.
2. You MUST use GNU Make to build your project and compile your source code into one executable named npshell. - The executable and Makefile should be placed at the top layer of the directory. We will use this executable for demo. - You are NOT allowed to demo if we are unable to compile your project with a single make command.
3. Upload only your code and Makefile. - Do NOT upload anything else (e.g. noop, removetag, test.html, .git , __MACOSX )
4. zip the directory and upload the .zip file to the E3 platform ATTENTION! We only accept .zip formate.g. Create a directory 0856000, the directory structure may be: 0856000 ├── Makefile ├── shell.cpp └── shell.h zip the folder 0856000 into 0856000.zip and upload 0856000.zip onto E3
5. Commit to BitBucket - Create a private repository with name: ${Your_Student_ID}_np_project1 inside the nctu_np_2019 team, and set the ownership to nctu_np_2019 . e.g. 0712345_np_project1 - You can push anything you need onto bitbucket (including removetag, noop, test.html ), but please make sure to commit at least 5 time .

We take plagiarism seriously.

• All projects will be checked by a cutting-edge plagiarism detector. You will get zero points on this project for plagiarism.
• Please don’t copy-paste any code from the internet, this may be considered plagiarism as well.
• Protect your code from being stolen.

Notes

• NP project should be run on NP servers (to be announced), otherwise, your account may be locked.
• Any abuse of NP server will be recorded.
• Don't leave any zombie processes in the system.
• You will lose points for violating any of the rules mentioned in this spec.
• Enjoy the project!