CS330 Assignment 1 Solution

CS330: Operating Systems
Implement mygrep which takes two arguments, a string and a path (file or directory). mygrep should search recursively for the given string in all regular files present in the directory sub-tree. It should output matching lines with full file path. You will submit a single C source file with implementation of mygrep.
The implementation of mygrep, when executed as ./mygrep Kanpur IITK should return output as mentioned under output format for the directory structure given in Figure 1. Here Kanpur and IITK are the string and path arguments, respectively.
The directory structure mentioned in Figure 1 is only for representation purpose and the actual test cases will have deeper directory structures.

Figure 1: Directory Structure
output format
IITK/Postgraduate/details.txt:Kanpur Postgraduate courses in Engineering offer Master of Technology (M.Tech), MS (R) and Ph.D. degrees ...
IITK/Undergraduate/info.txt:IIT Kanpur offers four-year B.Tech programs in Aerospace Eng ...
IITK/IITK Kanpur.txt:Faculty Building, IIT Kanpur ...
IITK/IITK Kanpur.txt:Under the guidance of economist John Kenneth Galbraith, IIT Kanpur was the first institute in India ...
You can use below mentioned APIs to implement this part of the assignment. Refer to man page of these APIs to know about their usage.
• opendir
• readdir
• closedir
• chdir
• open
• read
• close
• stat
2.1 @ operator
The @ operator takes two arguments, a string and a path. The program should output a number corresponding to count of lines that contain the string in the path provided.
The output of executing ./part2 @ Kanpur IITK should be equal to grep -rF Kanpur IITK | wc -l. This is the first check that you need to do. Here Kanpur and IITK are the string and path arguments, respectively.
You are free to use grep or your implementation of grep from part1 for this task.
2.2 $ operator
The $ operator takes four arguments, a string , a path, an output file and a command. You should get all lines that contain the string in the given path and write the result to output file as well as execute the command on the search result.
The output of executing ./part2 $ Kanpur IITK output.txt sort should be equal to grep -rF Kanpur IITK |tee output.txt | sort.
The output of executing ./part2 $ Kanpur IITK output.txt wc -l should be equal to grep -rF Kanpur IITK |tee output.txt | wc -l. This is the first check that you need to do. Here Kanpur and IITK are the string and path arguments respectively.
You are free to use grep or your implementation of grep from part1 for this task.
You can use below mentioned APIs to implement this part of the assignment. Refer to man page of these APIs to know about their usage.
• pipe
• dup, dup2
• fork
• exec
• open
Write a program to add up sizes of all files in the given directory. Your program will be provided with the path to the root directory (IITK Directory in Figure 2). It should perform the following actions
• Assume that there are N immediate child sub-directories under the root directory. For each immediate child sub-directory under the provided root directory, your program must fork a new process Pi(i will range from 1 to the total number of immediate child sub-directories) that recursively looks in all the sub-directories for the files and compute sum of their sizes.
• Your program should output the size of root directory as well as the size of all immediate child sub-directories.
• Let us see an example of the folder structure given in the Figure 2. We will be providing the path to root directory(IITK) has a command line argument to your program. The root directory is having two immediate child sub-directories (Postgraduate, Undergraduate). So your program has to fork two processes and add up the size of the files in its corresponding directories.

Figure 2: Folder Structure
• Your program should output the names of root, immediate child sub-directories and their corresponding size. The expected output of the Figure 2 directory structure is shown in Figure 3.

Figure 3: Expected output
• We have provided another sample explanation in the folder(Part 3Samples Explanation). You can also refer that.
3.1 Validation
Your submitted code will be validated based on the following criteria.
• If there are N immediate child sub-directories, your program should fork at least N process.
• There is no restriction on the number of pipes. You can create as many as it requires.
• In top of your file(part3.c) explain your implementation details and you should add comments to your code so that it will be helpful for us to go thorough your code if required.
• Before submitting the file, kindly verify your code with sample test cases which is provided in the directory ”Part 3Test Cases”.
3.2 Useful links
• http://www.cs.loyola.edu/ jglenn/702/S2005/Examples/dup2.html
• http://web.mst.edu/ ercal/284/PipeExamples/Pipe4.c
.
4 Submission guidelines
• You should name submission files as part1.c, part2.c and part3.c
• Source code for each part of the assignment should be placed in respective folders. For example, part1.c should be placed in /Assignment1/Part 1/src/. Don’t change the structure of Assignment1 folder. You need to submit a zip of the entire folder (Assignment1.zip)
• Source code should be properly commented.
• Some test cases for each part of the assignment are made available in respective folders (Test Cases). Passing of these test cases will fetch you some mark. We will use extra test cases as part of the evaluation to test the robustness of your implementation.