代写Network Programming Project 1 - NPShell代写留学生C/C++程序

日期：2024-03-30 10:18

Network?Programming?Project?1 -?NPShell

Deadline:?Wednesday,?2024/3/27?23:55

1 ???Introduction

In?this?project,?you?are?asked?to?design?a?shell?named?npshell.??The?npshell?should?support?the?following?features:

1. ?Execution?of commands

2. ?Ordinary?Pipe

3. ?Numbered?Pipe

4.?File?Redirection

More?details?will?be?defined?in?Section?3.

2 ???Scenario?of?using?npshell

2.1 ???Structure?of Working?Directory

Example:

working_dir	?
|?--?bin	#??Executables?may?be??added??to??or??removed??from??bin/
| ??????| -- ?cat	?
|???????|?--??ls	?
| ??????|--?noop	#??A?program??that??does?nothing
|???????| -- ?number	#??Add??a?number ?to??each??line??of??input
|???????| -- ?removetag	# ?Remove ?HTML ?tags??and??output ?to??STDOUT
|???????| -- ?removetag0 | --??test.?html	# ?Same ?as ?removetag, ?but ?outputs ?error??messages ?to ?STDERR
| --?npshell	?

2.2????Scenario

The?following?is?a?scenario?of using?the?npshell.

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???npshell???test.?html

% ?ls?bin

cat??????ls?????noop?????number?????removetag?????removetag0

%??cat??test.?html??>??test1.?txt

%??cat??test1.?txt

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???#?pipe??STDOUT ?to??the??first??command??of??next??line

%?number??????????????????????????????????# ?STDIN??is??from??the??previous??pipe??(removetag)

1

2??Test

3 ?This ?is??a??test?program

4??for??ras?.

5

%??removetag??test.?html??|2???#?pipe??STDOUT ?to??the??first??command??of??next?next??line

%??ls

bin ??npshell ??test1.txt ??test2.?txt???test.?html

%?number??????????????????????????????????# ?STDIN??is??from??the??previous??pipe??(removetag)?1

2??Test

3 ?This ?is??a??test?program

4??for??ras?.

5

%??removetag??test.?html??|2???#?pipe??STDOUT ?to??the??first??command??of??next?next??line

%??removetag??test.?html??|1???#?pipe??STDOUT ?to??the??first??command??of??next??line

# ?(merge ?with ?the?previous ?one)

%?number?????????????????????????????????# ?STDIN??is??from??the??previous??pipe??(both??two??removetag)

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

%??removetag??test.?html??|2??removetag??test.?html??|1??#?number?pipe?may ?occur ?in ?middle?% ?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

%??ls??|2

%??ls

bin ??npshell ??test1.txt ??test2.?txt???test.?html

%?number??>??test3.?txt

%??cat??test3.?txt

1?bin

2?npshell

3??test1.?txt

4??test2.?txt

5??test.?html

%??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 ?????????????# ?pipe ?both ?STDOUT ?and??STDERR

#??to??the??first??command??of??the?next??line

%?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?moves??the??executable ?"date" ?into ?$working_dir/bin/

%??date

Wed ?Mar??13??10:44:39 ?PM??CST??2024

% ?exit

bash$

3????Specification

3.1 ???NPShell?Behavior

1. ?Use?”%?”?as?the?command?line?prompt.?Notice?that?there?is?one?space?character?after?%.

2. ?The?npshell?parses?the?inputs?and?executes?commands.

3.?The?npshell?terminates?after?receiving?the?exit?command?or?EOF.

4.?There?will?NOT?exist?the?test?case?that?commands?need?to?read?from?STDIN.

3.2????Input

1. ?The?length?of?a?single-line?input?will?not?exceed?15000?characters.

2. ?The?length?of each?command?will?not?exceed?256?characters.

3. ?There?must?be?one?or?more?spaces?between?commands,?arguments,?pipe?symbol?(|),

rection?symbol?(>),?but?no?spaces?between?pipe?and?numbers?for?numbered-pipe.

Examples:

%??ls??-l??|???cat

%??ls??>?hello.?txt

% ?cat?hello.?txt??|4???????????????#?no??space??between??"| " ?and??"4"

% ?cat?hello.?txt??!4 ?????????????# ?no??space??between??"!" ?and??"4"

4. ?Only?English?alphabets?(uppercase?and?lowercase),?digits,?space,?newline,?”:”?,?”?>”?,?”?|?”?,?and?”!”?may?appear?in?test?cases.

3.3 ???Built-in?Commands

1. ?Format

.?setenv?[var]?[value]

Change?or?add?an?environment?variable.

If?var?does?not?exist?in?the?environment,?add?var?to?the?environment?with value.

If?var?already?exists?in?the?environment,?change?the?value?of?var?to?value.

Examples:

%??setenv ?PATH ?bin? ? ? ? ? ? ? ? ? ??# ?set??PATH??to??bin

% ?setenv ?PATH ?bin:npbin? ? ? ? ? ??# ?set??PATH??to?bin:npbin

.?printenv?[var]

Print?the?value?of an?environment?variable.

If?var?does?not?exist?in?the?environment,?show?nothing.

Examples:

% ?printenv ?LANG

en_US.?UTF-8

%?printenv?VAR1???????????????????# ?show?nothing ?if??the??variable??does?not ?exist

% ?setenv ?VAR1??test

% ?printenv ?VAR1

test

.?exit

Terminate?npshell.

2. ?Built-in?commands?will?appear?solely?in?a?line.

3.?Built-in?commands?will?not?pipe?to?other?commands,?and?no?commands?will?pipe?to?built-in commands.

3.4 ???Unknown?Command

1.?If?there?is?an?unknown?command,?print?error?message?to?STDERR?with?the?following?format:?Unknown?command: ?[command].

Examples:

%??ctt

Unknown ?command:???[ctt]?.

2.?You?do?not?need?to?print?the?arguments?of unknown?commands.

Examples:

% ?ctt??-n

Unknown ?command:???[ctt]?.

3. ?The?commands?after?unknown?commands?will?still?be?executed.

Examples:

% ?ctt??|???ls

Unknown ?command:???[ctt]?.

bin???npshell???test.?html

4. ?Messages?piped?to?unknown?commands?will?disappear.

Examples:

% ?ls??|???ctt

Unknown ?command:???[ctt]?.

3.5 ???Ordinary?Pipe?and?Numbered?Pipe

1.?You need to implement pipe?(cmd1?| ?cmd2), which means the?STDOUT?of the?left?hand?side

command?will?be?piped?to?the?right?hand?side?command.

Examples:

% ?ls??| ??cat?????# ?The??output??of??command??"ls"??acts??as??the??input??of??command??"cat"

bin

npshell

test.?html

2.?You need implement a special piping?mechanism,?called?numbered?pipe. ?There are?two?types?of?numbered?pipe?(cmd?|N?and?cmd?!N).

3. ?|N means the?STDOUT of the left?hand?side?command?will?be?piped?to?the?first?command?of?the?next?N-th?line, where?1?≤?N?≤?1000.

4. ?!N means both?STDOUT and STDERR?of the left?hand?side?command?will?be?piped?to?the?first?command?of?the?next?N-th?line, where?1?≤?N?≤?1000.

5.?If?|N?and?!N?occur?in?the?middle,?then?the?number?starts?counting?from?the?same?line.

6. ?The?line?with?build-in?command?or?unknown?command?also?counts?as?one?line?for?numbered?pipe,?but?the?empty?line?does?not.

Examples:

%??ls??|2

%??ctt

Unknown ?command:???[ctt]?.

% ?cat?????????????# ?The??output??of??command??"ls" ?acts??as??the??input??of??command??"cat"

bin

npshell

test.?html

%??ls??|2

%??setenv ?PATH ?bin

%?????????????????????# ?Press ?Enter

% ?cat?????????????# ?The??output??of??command??"ls" ?acts??as??the??input??of??command??"cat"

bin

npshell

test.?html

7.?When?the?output?of one?command?is?piped?(no?matter?ordinary?pipe?or?numbered?pipe),?it?is?likely?that?the?output?of this?command?exceeds?the?capacity?of the?pipe.?In?this?case,?you?still?need to?guarantee that?all?the?output?of this?command?is?piped?correctly.

Examples:

%??cat??large_file.?txt ?|??number???# ?All ?output??of ?"cat" ?should?be?piped ?correctly

%??cat??large_file.?txt ?|1 ????????????# ?All ?output ?of ?"cat" ?should?be?piped??correctly

%?number

(Hints:?You?can?think?about?when?the?npshell?should?wait?the?child?process.)

8. ?The?number?of piped?commands?may?exceed?the?maximum?number?of processes?that?one?user?can?run.?In?this?case, you?still?need?to?guarantee?that?all?commands?are?executed?properly.

Examples:

#??Suppose ?the?process??limit??is??512 ?and ?there??are??1000 ?"cat" ?in??one??line?.?#??All ?commands ?in??this ?line ?should?be ?executed?properly?.

%??ls ??|???cat??|???cat ??. ?.?.?.?.?. ???|???cat

bin

npshell

test.?html

9.?There?will?NOT?exist?the?test?case?that?one?pipe?is?full?and?needs?to?be?read?by?the?following?process?(not?forked?yet),?but?the?process?limit?is?reached.

3.6 ???File?Redirection

1.?You?need?to?implement?standard?output?redirection?(cmd?> file), which?means?the?output of the?command?will?be?written?to?files.

Examples:

#??The??output??of??command ?"ls"??is??redirected??to??file ?"hello.?txt"

%??ls??>?hello.?txt

%??cat?hello.?txt

bin

npshell

test.?html

2.?If the?file?already?exists,?the?file?should?be?overwritten?(not?append).

3.?You?do?not?need?to?handle?appending?for?standard?output?redirection?(>>).

4.?You?do?not?need?to?implement?standard?input?redirection?(<).

5.?You?do?not?need?to?implement?standard?error?redirection?(2>).

6.?You?do?not?need?to?handle?outputting?to?multiple?files?for?the?same?command.

7.?You?do?not?need?to?handle?outputting?to?both?the?file?and?the?pipe?for?the?same?command.?Examples:

%??ls??>??f1.?txt??>??f2.?txt?????????????????#??This?will?not?happen

%??ls??>?hello.?txt??| ??cat?????????????????# ?This??will?not?happen

%??ls??>?hello.?txt??|2 ?????????????????????# ?This?will?not?happen

% ?cat??f1.?txt??|??number??> ?f2.?txt????# ?This?may?happen

4 ???Requirements?and?Limitations

1.?You?can?only?use?C/C++ to?do this?project. ?Other third-party?libraries?are?NOT?allowed.

2.?In this?project,?system()?function?is?NOT?allowed.

3.?Except?for?the?three?built-in?commands?(setenv, printenv,?and?exit), you?MUST?use?the?exec family?of?functions?to?execute?commands.

4.?You?MUST?create?unnamed?pipes?to?implement?ordinary?pipe?and?numbered?pipe. ?Storing

data?into?temporary?files?is?NOT?allowed?for?ordinary?pipe?and?numbered?pipe.

5.?You?should?handle?the?forked?processes?properly,?or?there?might?be?zombie?processes.

6.?You?should?set the?environment variable?PATH to?bin/?and?./?initially.

Examples:

bash$ ?./npshell?????????????????????# ?execute??your?npshell

% ?printenv ?PATH ???????????????????????#??initial??PATH??is?bin/??and ?./

bin:?.

7.?You?should?NOT?manage?environment?variables?by?yourself.??Functions?like?getenv()?and?setenv()?are?allowed.

8.?The?commands?noop, ?number, ?removetag, ?and ?removetag0 ?are?offered?by?TA.?Please?download?them?from?E3?and?compile.

Examples:

g++?noop. cpp??-o??$working_dir/bin/noop

9.?The?executables?ls?and?cat?are?usually?placed?in?the?folder?/bin/?in?UNIX-like?systems.?You?can?copy?them?to?your?working?directory.

Examples:

cp??/bin/ls??/bin/cat??$working_dir/bin/

10. ?During?demo,?TA?will?prepare?these?commands?(executables)?for?you,?so?you?do?NOT?need?to?upload?them.??Besides,?TA?will?copy?additional?commands?to?bin/,?which?is?under?your working?directory.?Your?npshell?program?should?be?able?to?execute?them.

11.?We?will?use?NP?servers?for?demo. ??Make??sure??your??npshell??can??be??executed??in??NP servers.

5????Submission

.?E3:

(a) ?Create?a?directory?named?your?student?ID,?put?your?source?code?files?and?Makefile?into?the?directory.

DO?NOT?put?anything?else?in?it?(e.g.,?noop,?removetag,?test.html,?.git,???MACOSX).

(b)?You must provide a Makefile, which compiles your source code into one executable named?npshell with a single make?command. ?The Makefile?and the?executable?should?be?placed?at?the?top?layer?of the?directory.?We?will?use?this?executable?for?demo.

(c)?zip?the?directory?and?upload?the?.zip?file?to?E3.

Attention!!?we?only?accept?.zip?format

Example:

311581001

| --?Makefile

|--?npshell. cpp

|?.?.?.

Zip?the?folder?311581001?into?311581001.zip?and?upload?311581001.zip?to?E3

.?Bitbucket:

(a)??Create?a?private?repository?with?name: ?s{Your??Student?ID}?np?project1 inside?the?workspace?nycu?np?2024?and?the?project?np?project1?.

e.g.,??311581001_np_project1

(b)?You?can?push?anything?to?Bitbucket,?but?make?sure?to?commit?at?least?5?times.

6????Notes

1.?We?take?plagiarism?seriously.?You?will?get?zero?points?on?this?project?for?plagiarism.

2.?You?will?lose?points?for?violating?any?of the?rules?mentioned?in?this?spec.

3. ?NP?projects?should?be?run?on?NP?servers.?Otherwise,?your?account?may?be?locked.

4. ?Any?abuse?of NP?server?will?be?recorded.

5. ?Do?not?leave?any?zombie?processes?in?the?system.