代写SSE2310、代写c/c++编程

日期：2022-12-14 10:55

SSE2310/CSSE7231 — Semester 2, 2022

Assignment 3 (version 1.4)

Marks: 75 (for CSSE2310), 85 (for CSSE7231)

Weighting: 15%

Due: 6:00pm Friday 7th October, 2022

Specification changes are shown in red - version 1.0 to 1.1, blue - version 1.1 to 1.2,

green – version 1.2 to 1.3, magenta – version 1.3 to 1.4. Changes are summarised at the end of the document.

Introduction 1

The goal of this assignment is to demonstrate your skills and ability in fundamental process management and 2

communication concepts, and to further develop your C programming skills with a moderately complex program. 3

You are to create a program called jobthing, which creates and manages processes according to a job 4

specification file, and must monitor and maintain the status and input/output requirements of those processes. 5

The assignment will also test your ability to code to a programming style guide and to use a revision control 6

system appropriately. 7

CSSE7231 students will write an additional program, mytee which emulates some basic functionality of 8

the Unix tee command, as a further demonstration of your C programming, file and commandline handling 9

capabilities. 10

Student Conduct 11

This is an individual assignment. You should feel free to discuss general aspects of C programming and 12

the assignment specification with fellow students, including on the discussion forum. In general, questions like 13

“How should the program behave if 〈this happens〉?” would be safe, if they are seeking clarification on the 14

specification. 15

You must not actively help (or seek help from) other students or other people with the actual design, structure 16

and/or coding of your assignment solution. It is cheating to look at another student’s assignment code 17

and it is cheating to allow your code to be seen or shared in printed or electronic form by others. 18

All submitted code will be subject to automated checks for plagiarism and collusion. If we detect plagiarism or 19

collusion, formal misconduct actions will be initiated against you, and those you cheated with. That’s right, if 20

you share your code with a friend, even inadvertently, then both of you are in trouble. Do not post your 21

code to a public place such as the course discussion forum or a public code repository, and do not allow others 22

to access your computer – you must keep your code secure. 23

You must follow the following code referencing rules for all code committed to your SVN repository (not 24

just the version that you submit): 25

Code Origin Usage/Referencing

Code provided to you in writing this semester by

CSSE2310/7231 teaching staff (e.g. code hosted on Black-

board, posted on the discussion forum, or shown in class).

May be used freely without reference. (You must be able

to point to the source if queried about it.)

Code you have personally written this semester for

CSSE2310/7231 (e.g. code written for A1 reused in A3)

May be used freely without reference. (This assumes

that no reference was required for the original use.)

Code examples found in man pages on moss. May be used provided the source of the code is

referenced in a comment adjacent to that code. (Code

you have taken inspiration from must not be directly

copied or just converted from one programming

language to another.)

Code you have personally written in a previous enrolment

in this course or in another ITEE course and where that

code has not been shared or published.

Code (in any programming language) that you have taken

inspiration from but have not copied.

Other code – includes: code provided by teaching staff only

in a previous offering of this course (e.g. previous A1 solu-

tion); code from websites; code from textbooks; any code

written by someone else, or partially written by someone

else; and any code you have written that is available to

other students.

May not be used. If the source of the code is referenced

adjacent to the code then this will be considered code

without academic merit (not misconduct) and will be

removed from your assignment prior to marking (which

may cause compilation to fail and zero marks to be

awarded). Copied code without adjacent referencing will

be considered misconduct and action will be taken.

26

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Uploading or otherwise providing the assignment specification or part of it to a third party including online 27

tutorial and contract cheating websites is considered misconduct. The university is aware of these sites and 28

many cooperate with us in misconduct investigations. 29

The course coordinator reserves the right to conduct interviews with students about their submissions, for 30

the purposes of establishing genuine authorship. If you write your own code, you have nothing to fear from this 31

process. If you are not able to adequately explain your code or the design of your solution and/or be able to 32

make simple modifications to it as requested at the interview, then your assignment mark will be scaled down 33

based on the level of understanding you are able to demonstrate. 34

In short - Don’t risk it! If you’re having trouble, seek help early from a member of the teaching staff. 35

Don’t be tempted to copy another student’s code or to use an online cheating service. You should read and 36

understand the statements on student misconduct in the course profile and on the school web-site: https: 37

//www.itee.uq.edu.au/itee-student-misconduct-including-plagiarism 38

Specification – jobthing 39

jobthing reads a job configuration from a file whose name is provided as a command line argument. It creates 40

processes and runs programs according to that specification, optionally connecting those processes’ standard 41

input and output either to files, or jobthing itself via pipes. jobthing then reads input from stdin, interpreting 42

that input as commands that cause various actions to be taken, such as sending strings to the other processes, 43

reporting on statistics and so on. jobthing must handle certain signals and take specific action upon receiving 44

those signals. 45

Full details of the required behaviour are provided below. 46

Command Line Arguments 47

jobthing has one mandatory argument – the name of the job specification file, and also accepts several optional 48

arguments. These arguments may appear in any order. 49

./jobthing [-v] [-i inputfile] jobfile 50

The optional -v argument, if supplied, puts jobthing into verbose mode, causing it to emit additional 51

debug and status information. Precise requirements are documented below. 52

The optional -i inputfile argument is the name of a file which will be used to provide input to jobthing 53

and its managed processes. If no inputfile is specified (i.e. the -i argument is not given), then jobthing 54

is to take input from stdin. (Note that -i and -v are valid input file names – any string after -i is to be 55

treated as an input file name.) 56

The jobfile argument specifies the name of a file from which job information is to be read. This format 57

is documented below. This argument is mandatory. 58

If the user provides invalid options, too few or too many command line arguments, including repeated 59

arguments (e.g. -v -v), then jobthing shall emit the following usage information to stderr, and exit with 60

return code 1: 61

Usage: jobthing [-v] [-i inputfile] jobfile 62

If the inputfile specified with the -i argument is unable to be opened for reading, then the following message 63

should be emitted to stderr and jobthing should exit with return code 3: 64

Error: Unable to read input file 65

This should be checked prior to attempting to open the job file. 66

jobthing basic behaviour 67

jobthing reads the job specification file provided on the command line, spawning child processes and executing 68

programs as required. In general, jobthing is required to maintain a constant process state, regardless of what 69

happens to those child processes and programs. For example, if a child process is killed or terminates somehow, 70

then, unless otherwise specified, jobthing is required to notice this, and re-spawn the job as required, up to 71

the maximum number of retries specified for each job. 72

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Depending on the contents of the jobfile, each job created by jobthing may have its stdin and stdout 73

connected to a pipe (back to jobthing), or to a file on the filesystem. 74

Once jobthing has created the initial set of jobs, it is to take input either from stdin, or from the file 75

specified with the -i inputfile commandline argument, one line at a time. By default each input line should 76

be sent to each job to which jobthing has a pipe connection, however a line starting with the asterisk character 77

‘*’ will be interpreted as a command. 78

After sending the input text to each job, jobthing will then attempt to read a line of input from each 79

job (again, only those to which jobthing is connected by a pipe). Output received from jobs is emitted to 80

jobthing’s standard output. 81

Upon reading EOF from the input (stdin or the input file), jobthing shall terminate. 82

jobthing job parsing 83

The job file provided to jobthing is a text file, with one line per job. 84

85

If jobthing is unable to open the job file for reading, it is to emit the following message to stderr, and 86

exit with return code 2: 87

Error: Unable to read job file 88

Lines beginning with the ‘#’ (hash) character are comments, and are to be ignored by jobthing. Similarly, 89

empty lines (i.e. with no characters before the newline) are to be ignored. 90

91

All other lines are to be interpreted as job specifications, split over 4 separate fields delimited by the colon (‘:’) 92

character as follows 93

94

numrestarts:input:output:cmd [arg1 arg2 ...] 95

96

where each field has the following meaning or intepretation (where “empty” means a zero length string): 97

? numrestarts – specifies how many times jobthing shall start or restart this job if it terminates. 0 98

(zero) or empty implies that jobthing shall restart the job every time it terminates, 1 (one) means that 99

jobthing should attempt to launch the job once only upon startup – if it terminates it is not restarted. 100

Other integers are interpreted similarly. 101

input – empty implies that this job shall receive its standard input from a pipe connected to jobthing. 102

Otherwise, the named file is to be opened for reading and connected to this job’s standard input stream. 103

output – empty implies that this job shall send its standard output to a pipe connected to jobthing. 104

Otherwise, the named file is to be opened for writing (with flags O_CREAT | O_TRUNC and permissions 105

S_IWUSR | S_IRUSR) and connected to this job’s standard output stream. 106

cmd [arg1 arg2 ...] – the name of the program to be run for this job, and optional arguments to be 107

provided on the commandline to that program. Arguments are separated by spaces. Program names and 108

arguments containing spaces may be specified by enclosing them in double quotes. A helper function is 109

provided to make this easer, see the split_space_not_quote() function described on page 11. 110

Note: Individual job specifications are independent, and you do not need to consider if jobs might interact with 111

each other (e.g. sharing input or output files etc). We will only test job specifications that have predictable 112

and deterministic behaviour. 113

Note: The colon character has special meaning and will only appear in job files as a separator. You do not 114

need to consider, nor will we test for jobfiles that contain the colon character as part of a command name or 115

argument. 116

Note: See the split_line() function described on page 11 for an easy way to split the colon-delimited job 117

specifications. 118

119

Following are several sample jobfiles with explanatory comments:

# A job, running cat, stdin/stdout connected to jobthing. Only start 'cat' once

1:::cat

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# A job, running cat, stdin/stdout connected to jobthing. Start 'cat' a maximum of 5 times

5:::cat

# A job, running cat, stdin/stdout connected to jobthing.

# retries = 0 -> re-launch cat every time it terminates, no limit

0:::cat

# A job, running cat, take stdin from /etc/services, send stdout to foo.txt.

# Only run 'cat' once

1:/etc/services:foo.out:cat

# A job, running cat, take stdin from /etc/services, stdout connected back to jobthing

# Only run 'cat' once

1:/etc/services::cat

# two jobs, both running cat, stdin and stdout connected to jobthing.

# The first job runs cat only once, the second will restart it forever as required

1:::cat

0:::cat

If verbose mode is specified, for each valid job line read from the jobfile, jobthing should emit the following 120

output to its stdout 121

Registering worker N: cmd arg1 arg2 ... 122

where 123

N is the replaced with job number, incrementing from 1 (one) 124

cmd is the command to be run, and arg1, arg2, ... are any arguments provided to the command. Note 125

that there should be a single space between cmd and any arguments, and there should be no trailing space 126

on this line of output 127

The following is an example of such output: 128

Registering worker 1: cat

Registering worker 2: tee logfile.txt

A job line in the jobfile is invalid if any of the following conditions are met: 129

There are not precisely 4 fields separated by colons 130

The integer value first field (numrestarts) is not a proper, non-negative integer (if not empty) 131

The cmd field in the job line is empty or starts with a space 132

Invalid job lines are to be ignored and are not given job numbers. Further, if verbose mode is specifed on 133

the command line, then jobthing shall emit the following to its stderr: 134

Error: invalid job specification: 135

where is replaced by the offending job specification line, e.g. 136

Error: invalid job specification: -10:0:foobar baz 137

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jobthing startup phase 138

Once the jobfile has been read, jobs are to be created in the order they were specified in the job file. 139

? If an input file is specified for the job, jobthing shall attempt to open that file in read mode and the 140

job is to have its stdin redirected from that file. Otherwise, jobthing shall create a pipe, connecting 141

that job’s stdin to the reading end of the pipe, with jobthing holding the write end of the pipe through 142

which it will later send information. 143

Similarly, if an output file is specified for the job, jobthing shall attempt to open that file in for writing and 144

the job is to have its stdout redirected to that file. Otherwise, jobthing shall create a pipe, connecting 145

that job’s stdout to the writing end of the pipe, with jobthing holding the read end of the pipe through 146

which it will later receive information. 147

If a job has an input file specified, and that file cannot be opened, jobthing shall emit the following message 148

to stderr. The job shall be considered invalid unrunnable and no further handling or respawn attempts shall 149

be made for that job. (If an output file is also specified, no attempt shall be made to open it.) 150

Error: unable to open "" for reading 151

where is the name of the file from the job specification. 152

Similarly, if an output file is specified and cannot be opened for writing, the job is considered invalid 153

unrunnable, no further processing or spawn attempts are made, and jobthing shall emit to stderr: 154

Error: unable to open "" for writing 155

Once any input and output files and pipes are opened/created, jobthing shall spawn a new process for 156

each runnable job, connect the stdin and stdout of the new job as required, and then exec the command line 157

specified for the job. 158

If verbose mode is specified, then jobthing should emit the following to its stdout: 159

Spawning worker N 160

where N is replaced by the job number. 161

162

Important: jobthing shall ensure that all un-used file handles are closed before executing the job process. 163

That is, the job shall have only its standard input, output and error file handles open. (Standard error is just 164

to be inherited from jobthing.) Test scripts will check to ensure that no other file handles leak from jobthing 165

to individual jobs. 166

If the child’s exec call fails, the child process is to call _exit() with the return code 99. jobthing is not 167

expected to detect a failure to exec (e.g. such jobs don’t become unrunnable) – this is treated exactly the same 168

as a successful child execution where the child immediately returned exit status 99. 169

jobthing operation and command format 170

Once jobthing has started the jobs, it should sleep for one second and then enter an infinite loop (terminated 171

only by reading EOF on its input stream (stdin or the supplied input file) or by running out of viable workers 172

– see descriptions below). 173

Each time through the loop jobthing shall perform the following operations, in the exact order specified 174

below. 175

Note: Any jobs that were marked invalid unrunnable during the startup phase (i.e. because their input or 176

output files could not be opened) are excluded from all handling during this main loop. 177

1. Check on the status of each job (in the order they were specified in the job file), report on any jobs that 178

have terminated, and restart those which need to be restarted. 179

? for any jobs that have terminated since the last check, jobthing shall generate a line of output to 180

stdout in the following format: 181

Job N has terminated with exit code M 182

or 183

Job N has terminated due to signal S 184

depending on the reason for the job terminating. N, M and S should be substituted by the job number, 185

exit code or signal number as appropriate. 186

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close and clean up any pipes and file descriptors associated with communication to the terminated 187

job 188

for each job that has terminated, if the total number of times it has been (re-)started is less than the 189

maximum number specified in the job file, then the job shall be restarted in exactly the same way it 190

was started (including input/output file redirection/pipes as required). Note that it is possible that 191

a respawning might not be possible due to the inability to open an input or output file for reading 192

or writing (even though that succeeded for an earlier run). In this case, jobthing should print the 193

same error message as specified above (see “jobthing startup phase”) and make no further attempts 194

to respawn that job – i.e. the job becomes unrunnable. If the job is restarted and verbose mode is 195

specified, then jobthing shall emit the following to its stdout: 196

Restarting worker N 197

where N is replaced by the job number. 198

If a job has already been restarted the maximum number of times, then it should not be restarted – 199

the job is now unrunnable. 200

2. If jobthing determines that there are no jobs running and no further possible jobs left to (re)launch (all 201

jobs are unrunnable), then it shall emit the following message to stderr, and exit with exit code 0 (zero): 202

No more viable workers, exiting

Reasons for this are 203

No jobs remain with a non-zero restart count remaining 204

No jobs remain that have valid input or output redirection files 205

3. Read a line of input from stdin or the specific jobthing input file, and process it as a command according 206

to the following requirements: 207

If EOF is detected, then jobthing shall exit with exit status 0 (zero). 208

Lines beginning with the asterisk ‘*’ character are treated as commands – see below for details. After 209

processing the command, jobthing shall sleep for 1 second and then return to the top of the main 210

loop, checking job status again etc. (The same sleep/return applies to invalid commands also – in 211

this case the “processing” of the command means outputting an error message as described below.) 212

Any other lines are sent as-is to each job to which jobthing has a connection (i.e. a pipe exists 213

between jobthing and the job’s stdin). 214

Data sent to each job is to be echoed to jobthing’s stdout in the following format: 215

ID<-’text’ 216

where ID is the job ID (starting from one), and ’text’ is the line of input sent to the job, surrounded 217

by single quotes. 218

4. jobthing shall sleep for 1 second 219

5. jobthing shall attempt to read exactly one line of input from each job to which it has a pipe connected 220

to that job’s stdout. Each line of output received from each job shall be emitted to jobthing’s stdout 221

as follows: 222

ID->’text’ 223

where ID is the job ID (starting from one), and ’text’ is the line of output received from the job, 224

surrounded by single quotes. It is expected that jobs will have a line of output available. If a job fails to 225

send such a line it is acceptable for jobthing to block until such time as a line is returned (or EOF is 226

detected). If EOF is detected, no message is output unless verbose mode is enabled. If verbose mode is 227

enabled then jobthing should output the following to stderr: 228

Received EOF from job N 229

where N is replaced by the job number. 230

6. Otherwise, jobthing shall repeat the loop starting back at Step 1 above. 231

NOTE: it is critical that you do these actions in this order, otherwise your program will behave differently and 232

fail many tests. 233

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jobthing signal handling requirements 234

Upon receiving SIGHUP, jobthing is to emit to its stderr statistics on the history and status of each valid job 235

that was specified in the jobfile. Each line of the statistics report is of the format 236

237

jobnum:numstarts:linesto 238

where each field has the following interpretation: 239

jobnum – the number of the job, starting from one which is the first valid job in the provided jobfile 240

numstarts – how many times jobthing has attempted to start or restart the job, including the initial 241

process creation upon startup 242

linesto – how many lines of input jobthing has sent to the job. Jobs whose stdin is read from a file 243

(rather than a pipe from jobthing) will report 0 (zero). 244

Note that the statistics for any given job accumulate over multiple restarts – if a job is terminated and 245

respawned multiple times, the total number of lines sent to it over the lifetime of jobthing is reported. 246

jobthing shall block or otherwise ignore SIGINT (Control-C). 247

248

jobthing must gracefully handle the possibility that it attempts to write information down a pipe to a job that 249

has terminated. If this occurs, jobthing shall silently ignore this fact, and the terminated job and associated 250

pipes should be cleaned up as per normal processing, with the job being restarted if appropriate. 251

We will not test whether system calls are restarted following a signal – e.g. a sleep resulting from a *sleep 252

command can be shorter than expected if interrupted by a signal or can be resumed – either is acceptable. 253

jobthing command handling 254

The following table describes the commands that must be implemented by jobthing, and their syntax. Addi- 255

tional notes on each command will follow. 256

Command Usage Comments

*signal *signal jobID signum Send the signal (signum – an integer) to the given job(jobID).

*sleep *sleep millisec Sleep for millisec (an integer) milliseconds.

257

Any invalid commands provided to jobthing (i.e. a command word starting with ‘*’ is invalid), shall 258

result in the following message to stdout: 259

Error: Bad command 'cmd'

where ’cmd’ is the offending command enclosed in single quotes. (cmd is the text after the ‘*’ up until 260

the first space or newline – and may be an empty string.) 261

if the command is not provided the correct number of arguments, the following is emitted to stdout 262

Error: Incorrect number of arguments

All numerical arguments, if present, must be complete and valid numbers. e.g. “15” is a valid integer, but 263

“15a” is not. Your program must correctly identify and report invalid numerical arguments (see details 264

below for each command). Leading whitespace characters are permitted, e.g. “ 10” is a valid number – 265

these whitespace characters are automatically skipped over by functions like strtol() and strtod(). 266

Any text arguments, including strings and program names, may contain spaces if the argument is surrounded 267

by double quotation marks, e.g. "text with spaces". A line with an odd number of double quotes will 268

be treated as though there is an additional double quote at the end of the line1. A helper function is 269

provided to assist you with quote-delimited parsing, see the “Provided Library” section on page 11 for 270

usage details. 271

1This will not be tested

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*signal 272

The *signal command shall cause a signal to be sent to a job. Exactly two integer arguments must be specified 273

– the target job ID, and the signal number. 274

If the job ID is invalid, your program should emit the following to stdout: 275

Error: Invalid job

Reasons for a job number being invalid are: 276

an invalid integer, e.g. “23a” 277

an invalid job number (less than 1, greater than the total number of jobs) 278

the specified job is unrunnable has terminated or is otherwise invalid (reached maximum number of 279

restarts, input or output files could not be opened) 280

If the signal number is invalid (non-numeric, less than 1 or greater than 31) then your program should emit 281

the following to stdout: 282

Error: Invalid signal

If all arguments are valid, the signal shall be sent to the targetted job. (There is no need to check whether 283

the job is still running when the signal is actually sent.) 284

*sleep 285

The *sleep command shall cause jobthing to sleep for the specified number of milliseconds. Exactly one 286

non-negative integer argument must be provided. 287

If the sleep duration value is invalid (not a properly formed integer, or a negative value), your program 288

should emit the following to stdout: 289

Error: Invalid duration

If the arguments are valid, jobthing shall sleep for the required duration (in milliseconds). 290

Example jobthing Sessions 291

In this section we walk through a couple of increasingly more complex examples of jobthing’s behaviour. Note 292

however that these examples, like provided test-cases, are not exhaustive. You need to implement the program 293

specification as it is written, and not just code for these few examples. 294

Consider a config file once_cat.txt with following contents: 295

1 1:::cat

This defines a single job, running cat, to be launched once only, and stdin and stdout connected via pipes 296

to jobthing. We launch jobthing in verbose mode and interact with the job in some simple ways. Note that 297

text formatted in bold is entered and echoed on the terminal, it is not output of jobthing itself. 298

1 $./jobthing -v once_cat.txt

2 Registering worker 1:cat1: cat

3 Spawning worker 1

4 hello there

5 1<-'hello there'

6 1->'hello there'

7 this is some text

8 1<-'this is some text'

9 1->'this is some text'

Thus we see simple job startup, and text passing to and from the job. Next we can explore the *signal 299

command (continuing the same session): 300

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10 *signal 0 11

11 Error: Invalid job

12 *signal 1 45

13 Error: Invalid signal

14 *signal 23a 45

15 Error: Invalid job

16 *signal 1 9

17 WorkerJob 1 has terminated due to signal 9

18 No more viable workers, exiting

Here after several invalid *signal command attempts, we finally send signal 9 to worker 1, which causes 301

its termination. jobthing then determined that this job should only be launched once, and that with no more 302

viable runnable jobs to run it terminates. 303

We next consider job input and output redirection, with the file cat_once_in_out.txt: 304

1 1:/etc/services:./foo.out:cat

This job file runs a single job, cat, but it takes its standard input from /etc/services, and redirects its 305

output to ./foo.out. It runs only once. 306

Launching this job, in verbose mode, we see the following: 307

1 Registering worker 1: cat

2 Spawning worker 1

3 WorkerJob 1 has terminated with exit code 0

4 No more viable workers, exiting

In this example, we see that the process was spawned, but because its input was redirected from a file, the 308

cat process ran to completion almost immediately. This was detected by jobthing, which identified that no 309

further restarts should be attempted, and that no runnable jobs remained, so the program exits without pausing 310

for any user input. 311

Let’s now consider a more complex example, with multiple processes and different run counts. The example 312

configuration file is mixed_multicat.txt: 313

1 0:::cat

2 1:::cat

3 2:::cat

Here we have three jobs, all to run cat with their stdin and stdout connected via pipes to jobthing, 314

however each has a different number of restarts: zero (i.e. re-start endlessly), 1, and 2. 315

1 $./jobthing -v mixed_multicat.txt

2 Registering worker 1: cat

3 Registering worker 2: cat

4 Registering worker 3: cat

5 Spawning worker 1

6 Spawning worker 2

7 Spawning worker 3

8 Hello

9 1<-'Hello'

10 2<-'Hello'

11 3<-'Hello'

12 1->'Hello'

13 2->'Hello'

14 3->'Hello'

Entering a single line of input (’Hello’) has it sent to each job in turn, then that same string is returned 316

from each job by the cat process. 317

We then kill job number 2, and send some more input: 318

15 *signal 2 9

16 WorkerJob 2 has terminated due to signal 9

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17 Hello again

18 1<-'Hello again'

19 3<-'Hello again'

20 1->'Hello again'

21 3->'Hello again'

Here we see that job 2 was terminated and not restarted (its restart count was only 1), and that the 319

subsequent input (Hello again) was then only sent to remaining live jobs (1 and 3). Let’s send a signal to job 320

number 3, and send some more input: 321

22 *signal 3 11

23 WorkerJob 3 has terminated due to signal 11

24 Restarting worker 3

25 foobar

26 1<-'foobar'

27 3<-'foobar'

28 1->'foobar'

29 3->'foobar'

And again: 322

30 *signal 3 11

31 WorkerJob 3 has terminated due to signal 11

32 baz

33 1<-'baz'

34 1->'baz'

After the second signal, worker 3 has finally terminated and not restarted, and the input entered at the 323

console is sent only to worker 1. Since worker 1 has a restart count of zero (restart forever), we can send it as 324

many signals as we like, it will continue being restarted: 325

35 *signal 1 5

36 WorkerJob 1 has terminated due to signal 5

37 Restarting worker 1

38 *signal 1 6

39 WorkerJob 1 has terminated due to signal 6

40 Restarting worker 1

41 still there?

42 1<-'still there?'

43 1->'still there?'

Finally, let’s send SIGHUP to jobthing, and see the statistics reporting: 326

44 1:cat:2:4 1:3:5

45 2:cat:1:1 2:1:1

46 3:cat:2:3 3:2:3

Here we can see how many times each job was restarted (including expired ones like jobs 2 and 3), and how 327

many lines of input were sent to each. 328

Specification - mytee (CSSE7231 students only) 329

CSSE7231 students are to write an additional program, called mytee. mytee reads lines of input from stdin, 330

and writes them back out to stdout, and also to another file whose name is provided on the command line. By 331

default, mytee creates a new output file every time it is run, however this can be overridden by providing the 332

-a command line option. 333

Command Line Arguments 334

mytee requires one mandatory argument – the name of the output file, and accepts one optional argument. 335

These arguments may appear in any order. 336

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./mytee [-a] outfile 337

? The optional -a argument puts mytee into append mode. In this mode, if the specified output file already 338

exists, then mytee shall append content to it (add it at the end). Otherwise, and by default, mytee shall 339

overwrite the outfile. 340

? The outfile argument specifies the name of the file to which the input received from stdin should be 341

written. 342

Operation and errors 343

Once the required output file has been opened for writing (and possibly appending, depending on the presence 344

or absence of the -a option), mytee shall sit in an endless loop reading input one line at a time from stdin. 345

Each line of input should then be written to the output file, and also written to stdout. All output should be 346

flushed immediately to ensure predictable operation. 347

Upon receiving EOF on stdin, mytee shall terminate immediately with exit code 0. 348

If mytee is run with an invalid command line (incorrect, missing or additional arguments), it shall emit the 349

following usage message to stderr, and exit with return code 1: 350

Usage: mytee [-a] outfile 351

If mytee is unable to open the specified outfile for writing, it shall emit the follow to stderr, and return 352

exit code 2: 353

Error: unable to open for writing 354

where the string is replaced with the offending filename, for example 355

Error: unable to open /etc/services for writing 356

Provided Library: libcsse2310a3 357

A library has been provided to you with the following functions which your program may use. See the man 358

pages on moss for more details on these library functions. 359

char* read_line(FILE *stream); 360

The function attempts to read a line of text from the specified stream, allocating memory for it, and returning 361

the buffer. 362

char **split_line(char* line, char delimiter); 363

This function will split a line into substrings based on a given delimiter character. 364

char** split_space_not_quote(char *input, int *numTokens); 365

This function takes an input string and tokenises it according to spaces, but will treat text within double quotes 366

as a single token. 367

To use the library, you will need to add #include to your code and use the compiler flag 368

-I/local/courses/csse2310/include when compiling your code so that the compiler can find the include 369

file. You will also need to link with the library containing this function. To do this, use the compiler arguments 370

-L/local/courses/csse2310/lib -lcsse2310a3. 371

Style 372

Your program must follow version 2.2.0 of the CSSE2310/CSSE7231 C programming style guide available on 373

the course Blackboard site. 374

Hints 375

1. You may wish to consider the use of the standard library functions strtol(), and usleep() or nanosleep(). 376

2. While not mandatory, the provided library functions will make your life a lot easier – use them! 377

3. The standard Unix tee command behaves like cat, but also writes whatever it receives on stdin to a 378

file. This, combined with watch -n 1 cat in another terminal window, may be very helpful 379

when trying to figure out if you are setting up and using your pipes correctly. 380

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4. You can examine the file descriptors associated with a process by running ls -l /proc/PID/fd where PID 381

is the process ID of the process. This may be helpful to ensure you are closing all required file descriptors 382

before executing jobs. 383

5. Review the lectures/contacts from weeks 6 and 7. These cover the basic concepts needed for this assign- 384

ment and the code samples may be useful. Similarly, the Ed Lessons exercises for weeks 6 and 7 may be 385

useful. 386

Suggested Approach 387

It is suggested that you write your program using the following steps. Test your program at each stage and 388

commit to your SVN repository frequently. Note that the specification text above is the definitive description 389

of the expected program behaviour. The list below does not cover all required functionality. 390

1. Write small test programs to figure out the correct usage of the system calls required for each jobthing 391

command – i.e. how to connect both stdin and stdout of a child process to pipes and manage access to 392

them from the parent. (This is essentially what the week 6 and 7 Ed Lessons exercises ask you to do.) 393

2. Write the initial job spawning capability of jobthing. 394

3. Add the required input/output setup for each job. 395

4. Add the main loop functionality – implement the basic input/output functionality of jobthing first, and 396

make sure you can talk to the jobs. Then extend that to add command processing as a special case. 397

Forbidden Functions 398

You must not use any of the following C functions/statements. If you do so, you will get zero (0) marks for the 399

assignment. 400

goto 401

longjmp() and equivalent functions 402

system() or popen() 403

mkfifo() or mkfifoat() 404

Submission 405

Your submission must include all source and any other required files (in particular you must submit a Makefile). 406

Do not submit compiled files (e.g. .o files and compiled programs). 407

Your programs jobthing and mytee (CSSE7231 only) must build on moss.labs.eait.uq.edu.au with: 408

make 409

Your program must be compiled with gcc with at least the following options: 410

-pedantic -Wall -std=gnu99 411

You are not permitted to disable warnings or use pragmas to hide them. You may not use source files other 412

than .c and .h files as part of the build process – such files will be removed before building your program. 413

CSSE7231 only - The default target of your Makefile must cause both programs to be built2. 414

If any errors result from the make command (i.e. no executable is created) then you will receive 0 marks 415

for functionality (see below). Any code without academic merit will be removed from your program before 416

compilation is attempted (and if compilation fails, you will receive 0 marks for functionality). 417

Your program must not invoke other programs or use non-standard headers/libraries other than those 418

explicity described in this specification. 419

Your assignment submission must be committed to your subversion repository under 420

https://source.eait.uq.edu.au/svn/csse2310-sem2-sXXXXXXX/trunk/a3 421

2If you only submit an attempt at one program then it is acceptable for just that single program to be built when running make.

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where sXXXXXXX is your moss/UQ login ID. Only files at this top level will be marked so do not put source 422

files in subdirectories. You may create subdirectories for other purposes (e.g. your own test files) but these 423

will not be considered in marking – they will not be checked out of your repository. 424

You must ensure that all files needed to compile and use your assignment (including a Makefile) are com- 425

mitted and within the trunk/a3 directory in your repository (and not within a subdirectory or some other part 426

of your repository) and not just sitting in your working directory. Do not commit compiled files or binaries. 427

You are strongly encouraged to check out a clean copy for testing purposes. 428

To submit your assignment, you must run the command 429

2310createzip a3 430

on moss and then submit the resulting zip file on Blackboard (a GradeScope submission link will be made 431

available in the Assessment area on the CSSE2310/7231 Blackboard site)3. The zip file will be named 432

sXXXXXXX_csse2310_a3_timestamp.zip 433

where sXXXXXXX is replaced by your moss/UQ login ID and timestamp is replaced by a timestamp indicating 434

the time that the zip file was created. 435

The 2310createzip tool will check out the latest version of your assignment from the Subversion repository, 436

ensure it builds with the command ‘make’, and if so, will create a zip file that contains those files and your 437

Subversion commit history and a checksum of the zip file contents. You may be asked for your password as 438

part of this process in order to check out your submission from your repository. 439

You must not create the zip file using some other mechanism and you must not modify the zip file prior 440

to submission. If you do so, you will receive zero marks. Your submission time will be the time that the file 441

is submitted via GradeScope on Blackboard, and not the time of your last repository commit nor the time of 442

creation of your submission zip file. 443

We will mark your last submission, even if that is after the deadline and you made submissions before the 444

deadline. Any submissions after the deadline4 will incur a late penalty – see the CSSE2310/7231 course profile 445

for details. 446

Marks 447

Marks will be awarded for functionality and style and documentation. Marks may be reduced if you are asked 448

to attend an interview about your assignment and you are unable to adequately respond to questions – see the 449

Student conduct section above. 450

Functionality (60 marks) 451

Provided your code compiles (see above) and does not use any prohibited statements/functions (see above), and 452

your zip file has been generated correctly and has not been modified prior to submission, then you will earn 453

functionality marks based on the number of features your program correctly implements, as outlined below. 454

Partial marks will be awarded for partially meeting the functionality requirements. Not all features are of equal 455

difficulty. If your program does not allow a feature to be tested then you will receive 0 marks for 456

that feature, even if you claim to have implemented it. For example, if your program can never create a child 457

process then we can not test your communication with that job, or your ability to send it signals. Memory- 458

freeing tests require correct functionality also – a program that frees allocated memory but doesn’t implement 459

the required functionality can’t earn marks for this criteria. This is not a complete list of all dependencies, 460

other dependencies may exist also. If your program takes longer than 15 seconds to run any test, then it will be 461

terminated and you will earn no marks for the functionality associated with that test. The markers will make 462

no alterations to your code (other than to remove code without academic merit). 463

Functionality marks (out of 60) will be assigned for jobthing in the following categories (CSSE2310 and 464

CSSE7231): 465

1. jobthing correctly rejects invalid command lines and handles inability to open files (3 marks) 466

2. jobthing correctly starts jobs and sets up their input and output correctly (including pipes) 467

(includes handling comments in job files and invalid job specifications) (12 marks) 468

3You may need to use scp or a graphical equivalent such as WinSCP, Filezilla or Cyberduck in order to download the zip file to

your local computer and then upload it to the submission site.

4or your extended deadline if you are granted an extension.

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3. jobthing correctly handles jobthing standard input (or inputfile) text (non commands 469

and invalid commands) (9 marks) 470

4. jobthing correctly handles and identifies the termination of child jobs and their causes 471

(including restarting jobs when appropriate) (8 marks) 472

5. jobthing correctly closes all unnecessary file handles in child processes (4 marks) 473

6. jobthing correctly implements *signal command and argument error checking (7 marks) 474

7. jobthing correctly implements *sleep command and argument error checking (5 marks) 475

8. jobthing correctly handles SIGHUP and emits job statistics (5 marks) 476

9. jobthing correctly handles SIGPIPE and SIGINT as appropriate (2 marks) 477

10. jobthing frees all allocated memory prior to exit (when exiting under normal circumstances, 478

i.e. EOF received on jobthing’s stdin, or no viable jobs remain) (5 marks) 479

Note that verbose mode functionality is covered in multiple categories. 480

Functionality marks (out of 10) will be assigned for mytee in the following categories (CSSE7231 only): 481

11. mytee correctly rejects invalid command lines (3 marks) 482

12. mytee correctly handles errors with output files (2 marks) 483

13. mytee correctly duplicates input onto stdout and the required output file (3 marks) 484

14. mytee correctly handles appending to output files (2 marks) 485

Some functionality may be assessed in multiple categories, e.g. the ability to launch jobs must be working to 486

test more advanced functionality. Your programs must not create any files other than those possibly specified 487

as output redirection for jobs, or files created by the jobs themselves. Doing otherwise may cause tests to fail. 488

Style Marking 489

Style marking is based on the number of style guide violations, i.e. the number of violations of version 2.2 of 490

the CSSE2310/CSSE7231 C Programming Style Guide (found on Blackboard). Style marks will be made up of 491

two components – automated style marks and human style marks. These are detailed below. 492

You should pay particular attention to commenting so that others can understand your code. The marker’s 493

decision with respect to commenting violations is final – it is the marker who has to understand your code. To 494

satisfy layout related guidelines, you may wish to consider the indent(1) tool. Your style marks can never be 495

more than your functionality mark – this prevents the submission of well styled programs which don’t meet at 496

least a minimum level of required functionality. 497

You are encouraged to use the style.sh tool installed on moss to style check your code before submission. 498

This does not check all style requirements, but it will determine your automated style mark (see below). Other 499

elements of the style guide are checked by humans. 500

All .c and .h files in your submission will be subject to style marking. This applies whether they are 501

compiled/linked into your executable or not5. 502

Automated Style Marking (5 marks) 503

Automated style marks will be calculated over all of your .c and .h files as follows. If any of your submitted 504

.c and/or .h files are unable to be compiled by themselves then your automated style mark will be zero (0). 505

(Automated style marking can only be undertaken on code that compiles. The provided style.sh script checks 506

this for you.) 507

If your code does compile then your automated style mark will be determined as follows: Let 508

W be the total number of distinct compilation warnings recorded when your .c files are individually built 509

(using the correct compiler arguments) 510

5Make sure you remove any unneeded files from your repository, or they will be subject to style marking.

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