CS270 – System Software Homework #4
Linux program代写 For this assignment you are to build a Linux program that employs cooperating processes to accomplish specified tasks.
Fall 2018
Due on or before October 28 at 11:59:59 PM
For this assignment you are to build a Linux program that employs cooperating processes to accomplish specified tasks. We won’t be able to use pipes or sockets since we haven’t coveredthem yet, but it should be a fun assignment regardless. Your program must be written in Your program will be compiled and tested on cs-course36.cs.uidaho.edu, so you should at least test it there before you turn it in.
1 The Program Linux program代写
The program that you are going to build is called ptor. A brief description of ptor follows:
usage: ptor
The ptor program is used to perform tasks that are specified by the user. The tasks that can be performed are described in the section titled ”User Commands.”
1.1 Program Options
The ptor program does not take any command-line options.Linux program代写
1.2 Program Mechanics
The ptor program is composed of two processes that cooperate to accomplish tasks that are specified by the user. The two processes are referred to in this document as the parent and thechild. The typical ptor user has no idea that two processes are used to accomplish the specified tasks. The interplay between the parent and child processes are of particular importance to you, however, since you will be building ptor rather than just using it. The parent and child processes communicate via Linux signals, and send and receive data from one another using text files. The ptor program creates two text files, one named ”ptor-parent-NN” where NN is replaced with the PID of the parent process, and another named ”ptor-child-NN” where NN is replaced with the PID of the child process. These two files are hereafter referred to as ptor-parent-file and ptor-child-file respectively.Linux program代写
The following list specifies the mechanics of the interplay between the cooperating processes that are used to execute user commands. This interplay is very important.
You should study this list carefully, and build your program so that it behaves as specified in this list.
- Userlaunches ptor on the shell command-line
- Parentprocess executes system call to create child process
- Parentprocess waits to receive SIGUSR1 signal from child process
- Childprocess, when ready, sends SIGUSR1 signal to parent process
- Parentprocess emits a command prompt of the form “cmd: ” and waits for the user to enter a command.Linux program代写
- Userenters command.
- Parentprocess checks command. If command is “exit”, GOTO Step 16 below.
- Parentprocess writes the specified command to ptor-parent-file.
- Parentsends SIGUSR1 signal to child.
- Childprocess, upon receiving the SIGUSR1 signal, opens ptor-parent-file and processes the command contained
25.Childprocess interprets and executes the specified command.
26.Childprocess writes the result of executing the specified command into ptor-child-file.
27.Childprocess sends signal SIGUSR2 to parent process.
28.Parentprocess, upon receipt of the SIGUSR2 signal, opens ptor-child-file, reads the result contained therein, and displays the result to the user.
A newline character is appended to the result (if necessary) to keep things neat and tidy for the user.Linux program代写
29.GOTOStep 5 above.
30.Parentprocess sends SIGUSR2 signal to child process and waits for child process to terminate.
31.Childprocess, upon receipt of signal SIGUSR2, terminates with an exit status that is the count of the number of invalid commands that the user specified during the current session.Linux program代写
32.Whenchild process terminates, parent process emits message of the form “ptor: terminating with status NN” where NN is replaced with the exit status of the child process.
33.Parentprocess exits with status NN, the same exit status as the child process.
1.3 User Commands Linux program代写
The following describes the tasks that ptor can be used to accomplish. If the user specifiesany command other than those that are listed below, ptor will emit a message of the form “ptor: Invalid command” and continue processing commands.
- Hfname fname2 This command is used to specify that ptor should compute and displaythe Hamming distance between the files named fname and fname2. The files namedfname and fname2 must be the same siz If the file sizes differ, ptor will emit a message of the form “ptor: H: file sizes differ” to stdout.
If the file sizes do not differ, ptor will compute the bitwise Hamming distance betweenfname and fname2 and print the result to stdout. The result printed will be of the form”ptor: H: Hamming distance: NN”, where NN is the computed bitwise Hamming dis- tance.Linux program代写
- Ou This command is used to determine the next number that contains the same number of ‘1’ bits as u, where u is an unsigned integral number in decimal.
The following is an example of this command in action:
-bash-4.1$ ./ptor cmd: O 4
ptor: O: 8
cmd: O 17
ptor: O: 18 Linux program代写
cmd: O 10
ptor: O: 12 cmd: exit
ptor: terminating with status 0
-bash-4.1$
- Rfname This command is used to specify that ptor should identify the longest run (as per Run-Length Encoding, or RLE) of bytes contained in fname. ptor prints the 0-based location of the byte that starts the run, the value of the byte contained within the run, and the 1-based length of the run to stdout. The location of the run and the length of the run are printed in base 10, while the value of the byte contained within the run is printed in base Linux program代写
The following is an example of the output by this option when invoked on a file in which the longest run starts at 0-based byte 72. The run has a length of 113 bytes, and the value of the byte contained within the run is the space (32 or 0x20) character:
ptor: R: 72 0x20 113
- Xfname This command is used to specify that ptor should calculate and print the checksum of the bytes in the file named fname. The checksum calculated by ptor for this op- tion is a “modular summation” This checksum is calculated by summing all the bytes in the file fname, ignoring any overflow, and then performing a two’s comple-ment of the sum to produce the final result. The result calculated by this option is printedto stdout and will be of the form: “ptor: X: 0xXX” where XX (base 16) is the calculated checksum for the file fname.Linux program代写
- + b1 b2 This command is used to specify that ptor should add the two binary num- bers b1 and b2 and print the result. The binary numbers b1 and b2 need not be the samelength.The ptor program places no upper bound on the maximum size of binary numbers that can be added. The result calculated by this command is printed to stdout and will be of the form: “ptor: +: bb” where bb (base 2) is the calculated sum.
The following is an example of this command in action:
-bash-4.1$ ./ptor cmd: + 11101 1
ptor: +: 11110
cmd: + 111111111111111111111111111111111111111111111111111111111111111111 1
ptor: +: 1000000000000000000000000000000000000000000000000000000000000000000
cmd: exit
ptor: terminating with status 0 Linux program代写
-bash-4.1$
- !This command is used to specify that ptor should emit a message containing the count of valid and invalid commands that have been encountered in the current session. The message emitted by this command will be of the form: “ptor: !: X valid Y invalid” where X and Y are the count of valid and invalid commands, respectively, that have been encountered so This count includes the ! command that is currently executing. The following is an example of this command in action:
-bash-4.1$ ./ptor cmd: R /tmp/ktpg.svg
ptor: R: file not found cmd: R ~/tmp/ktpg.svg ptor: R: 148915 0xec 2177 cmd: x: ~/tmp/ktpg.svg ptor: Invalid command cmd: X: /tmp/kipg.svg ptor: X: 0x3a
cmd: !
ptor: !: 4 valid 1 invalid cmd: exit
ptor: terminating with status 1
-bash-4.1$
2 Submitting Your Program
You must submit your program using cscheckin. You must create and submit a Makefilewith your source code. This Makefile will be used to build your program. Please placeyour code files and Makefile in a tar archive named hw4.tar. Please do not compress yourprogram using zip, gzip, winzip, winrar, or any other compression tool before or after mak- ing a tar archive for submission. When you have finished testing your program, please usecscheckin to submit the hw4.tar file to your instructor.
3 Grading Linux program代写
Youmust do your own work for this assignment. This is not a “team programming” exercise. All code submitted for this assignment must be entirely your own. Your program must use cooperating processes and behave precisely as specified in this assignment. Your program will be evaluated for completeness, clarity, efficiency, and compliance with the specified require- ments.
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