{ "cells": [ { "cell_type": "markdown", "id": "fb2efee8-a9e6-4254-a017-94905bb0aa63", "metadata": {}, "source": [ "

Lab II: IPC and pthreads Library

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INSTRUCTIONS
\n", "" ] }, { "cell_type": "markdown", "id": "269360d6-3f03-4b79-8905-c38281fececf", "metadata": {}, "source": [ "
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Task 1

\n", "Write a program to do the following\n", "
    \n", "
  1. Opens a pipe
    2. \n", "
  2. Creates a child process
    3. \n", "
  3. The parent process opens the file /etc/passwd and writes\n", " it one line at time into the pipe
    4. \n", "
  4. Once the contents of the file are completely written, the parent\n", " process closes the pipe and waits for the child process to\n", " terminate
    5. \n", "
  5. The parent process prints the word Done! and then terminates\n", " after the child process has terminated
    6. \n", "
  6. The child process reads the pipe, and writes the contents on to the\n", " terminal, prefixing each line with its line number and the word, \n", " Child:
    7. \n", "
  7. The child process terminates when there is no more content to be read\n", " from the pipe
    8. \n", "
\n", "Use the code stub given in the cell below.\n", "

Insert the required code and run the cell to save the contents into the file\n", "lab02_task1.c. DO NOT CHANGE THE FIRST LINE in the cell.

\n", "

Compile the code in the cell below the code cell and run it. Make sure you get the correct output.

" ] }, { "cell_type": "code", "execution_count": null, "id": "78c4b185-c3d4-45b4-bdeb-9529a1bfda3d", "metadata": {}, "outputs": [], "source": [ "%%file lab02_task1.c\n", "#include \n", "#include \n", "#include \n", "#include \n", "#include \n", "#include \n", "\n", "#define READ 0\n", "#define WRITE 1\n", "#define MAXLEN 80\n", "\n", "int main(int argc, char *argv[])\n", "{\n", " int p[2], pid, lnum;\n", " char buffer[MAXLEN];\n", " FILE *fp;\n", "\n", " /* Insert code to open pipe and check for error in opening it */\n", "\n", " if ((pid = fork()) == 0) { /* Child Process */\n", " lnum = 1; /* For printing line numbers */\n", " /* Insert code to read from pipe */\n", " \n", " } else { /* Parent Process */\n", " /* Open the file /etc/passwd for reading; check for errors */\n", "\n", " /* Insert code for reading from the file and writing into the pipe */ \n", "\n", " /* Be a good programmer and close all open files and descriptors */\n", " close(p[WRITE]);\n", " fclose(fp);\n", " /* Wait for child to complete its job and terminate */\n", " waitpid(pid, NULL, 0);\n", "\n", " printf(\"Done!\\n\");\n", " }\n", "\n", " exit(0);\n", "}" ] }, { "cell_type": "code", "execution_count": null, "id": "ee076eab-8667-4510-88ea-aaa1811237b5", "metadata": {}, "outputs": [], "source": [ "%%bash\n", "gcc lab02_task1.c -o lab02_1" ] }, { "cell_type": "code", "execution_count": null, "id": "88e1bfb3-9d79-4802-84f3-db4e5e14aeee", "metadata": {}, "outputs": [], "source": [ "%%bash\n", "./lab02_1 lab02_task1.c" ] }, { "cell_type": "markdown", "id": "904fc6a2-f9bc-454b-b6f9-39fb92a0604b", "metadata": {}, "source": [ "
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Task 2

\n", "In this task, you will use a named pipe (FIFO) and see how it is\n", "similar as well as different from a file. Do the following\n", "
    \n", "
  1. Create a named pipe called <your roll number>_fifo using the\n", " following command in a terminal\n", "
    mknod <your roll number>_fifo p
    2. \n", "
  2. Write a program to read the contents of the named pipe in the cell\n", " below. You can treat the named pipe exactly as a regular file\n", " including the use of FILE * file pointer for opening it.
    3. \n", "
  3. Save it by running the cell and compile it in the next cell\n", " below it.
    4. \n", "
  4. Open at least two terminals. In one terminal run your program by typing\n", " ./lab02_2 in it. What happened?
    5. \n", "
  5. Go to the other terminal and copy the file lab02_task1.c\n", " to your named pipe. What happened now?
    6. \n", "
  6. Repeat the above step to copy /etc/passwd again into your named pipe.\n", " What happened now?
    7. \n", "
  7. What is the size of your named pipe? Type ls -l for the\n", " answer.
    8. \n", "
" ] }, { "cell_type": "code", "execution_count": null, "id": "9d2b0bca-ec92-4989-adc0-c5d169450ecc", "metadata": {}, "outputs": [], "source": [ "%%file lab02_task2.c\n", "#include \n", "#include \n", "\n", "#define MAXLEN 80\n", "\n", "int main(void)\n", "{\n", " FILE *mpp;\n", " char buffer[MAXLEN];\n", "\n", " /* Insert code to open the named pipe and read from it */\n", "\n", " /* Insert code to write the contents of the pipe to terminal */\n", "\n", " fclose(mpp); /* We are good students!! */\n", " exit(0);\n", "}" ] }, { "cell_type": "code", "execution_count": null, "id": "b064a23d-ac93-4d33-abf8-7a0b84fb8e5a", "metadata": {}, "outputs": [], "source": [ "%%bash\n", "gcc lab02_task2.c -o lab02_2" ] }, { "cell_type": "code", "execution_count": null, "id": "b07d8bdb-ce6a-4f09-8f6a-577849fcc82e", "metadata": { "scrolled": true }, "outputs": [], "source": [ "%%bash\n", "./lab02_2" ] }, { "cell_type": "markdown", "id": "0cc6a460-76a5-4171-bb84-f3b23a6d131d", "metadata": {}, "source": [ "
\n", "

Task 3

\n", "In this task, you will see how threads share the address space of the parent process and compare the results with those obtained with parent and child processes. For this task, you need to create three threads. Each thread will modify its variables and output them. Analyse the results to understand how threads work.\n", "
    \n", "
  1. Look at the code below that creates one thread from the main process.
    2. \n", "
  2. Create two threads that call the function wfile
    3. \n", "
  3. Complete the thread function so that it writes into a file.
    4. \n", "
  4. Create a third thread that runs the function chg_var(). See\n", " how we modify the parameter passed to it. Understand it.
    5. \n", "
  5. Once the program terminates, examine the file to see how the threads\n", " write into the file.
    6. \n", "
  6. Look at the values printed for the variables.
    7. \n", "
  7. Run the program several times and see how the results change.
    8. \n", "
" ] }, { "cell_type": "code", "execution_count": null, "id": "0c494c09-251c-4525-bd9a-01ca66d8f531", "metadata": {}, "outputs": [], "source": [ "%%file lab02_task3.c\n", "#include \n", "#include \n", "#include \n", "#include \n", "#include \n", "\n", "#define MAXTHREADS 6\n", "\n", "void *wfile(void *), *chgvar(void *);\n", "char *extstring;\n", "\n", "void *wfile(void *wp)\n", "{\n", " int i;\n", "\n", " /* Insert code here to write 100 lines of text into the file given\n", " by *wp */\n", "\n", " return(NULL);\n", "}\n", "\n", "void *chg_var(void *rv)\n", "{\n", " *(int *)rv = *(int *)rv * 7; /* Ugly (or beautiful)! */\n", "\n", " return(NULL);\n", "}\n", "\n", "int main(void)\n", "{\n", " int regvar=25, i=0, j=0;\n", " pthread_t tid[MAXTHREADS];\n", " FILE *fp;\n", "\n", " extstring = malloc(24);\n", " strcpy(extstring, \"Hello, World!\");\n", "\n", " /* Insert code here to open a file \"thread_outputs.txt\" for writing */\n", "\n", " /* Code to create a single thread running the funtion wfile.\n", " Modify the code to create two threads */\n", " if ((pthread_create(&tid[i++], NULL, wfile, (void *)fp)) != 0) {\n", " printf(\"Error in creating the first thread\\n\");\n", " exit(1);\n", " }\n", "\n", " /* Create a third thread here to run the function chg_var */\n", "\n", " /* Let us wait for all threads to return */\n", " while (j < i) {\n", " pthread_join(tid[j++], NULL);\n", " }\n", " printf(\"Regvar: %d\\tExtvar: %s\\n\", regvar, extstring);\n", " fclose(fp);\n", " exit(0);\n", "}" ] }, { "cell_type": "code", "execution_count": null, "id": "e556b6b1-14d0-42b5-93b5-1ae36b0f6066", "metadata": {}, "outputs": [], "source": [ "%%bash\n", "gcc lab02_task3.c -o lab02_3 -lpthread" ] }, { "cell_type": "code", "execution_count": null, "id": "149f68a7-794d-4f99-9b50-19cddd347c53", "metadata": {}, "outputs": [], "source": [ "%%bash\n", "./lab02_3" ] }, { "cell_type": "markdown", "id": "e3e0e902-6200-44ad-84e3-c7ea21595eec", "metadata": {}, "source": [ "
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THE END
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