Assignment 9: Trust the Process

Due Friday, March 27, at midnight

The goals for this assignment are:

  • Gain experience working with fork and exec.

  • Implement a multi-process program

Update your repository

Do a git pull to obtain the basecode for this assignment.

Your repository should now contain a new folder named A09.

1. Grep

In the file, grep.c, implement a program that uses N processes to search for a keyword in a set of files.

Your program implements a simplified version of the bash command grep. Grep searches a list of files for a given keyword or expression. For example, the following command searches for the keyword public in a list of source files. We use the find command to generate the list of source files to search. For example:

grep
Make sure you include the backticks, e.g. ` . This adds the filenames found by find as command line arguments to grep. 
$ make grep
gcc -g -Wall -Wvla -Werror grep.c -o grep
$ ./grep
usage: ./grep <NumProcesses> <Keyword> <Files>
$ ./grep 1 class missing.txt
Searching 1 files for keyword: class
Process [613] searching 1 files (3 to 4)
Process [613] Error: Cannot open file
Total occurances: 0
Elapsed time is 0.000608
grep fork

Requirements:

  • Your program should take the number of processes, keyword, and a list of files as command line arguments

  • Subdivide the files among the N processes. Note that the number of files may not divide evenly between processes.

  • Print the totals and sub-division of files similarly to the output above

  • Use the fgets function to process the lines in each file

  • Use the function strstr defined in string.h to search lines of text for the keyword. Documentation is here

  • To compute the total count, each child process can return the number matching lines using its exitcode. Recall that the parent can use the status reported by waitpid to get the children’s exit code.

  • Your program should report the amount of time needed to search using gettimeofday

You can print with colors to the console using ANSI escape sequences (see below). For example, printf(ANSI_COLOR_GREEN "Green Text" ANSI_COLOR_RESET); will print green text. Here is a good guide! 
// Helpful macros for working with color
#define ANSI_COLOR_RED     "\x1b[31m"
#define ANSI_COLOR_GREEN   "\x1b[32m"
#define ANSI_COLOR_YELLOW  "\x1b[33m"
#define ANSI_COLOR_BLUE    "\x1b[34m"
#define ANSI_COLOR_MAGENTA "\x1b[35m"
#define ANSI_COLOR_CYAN    "\x1b[36m"
#define ANSI_COLOR_RESET   "\x1b[0m"

2. Personal Shell

In the file, shell.c, implement a program that implements a simple shell.

RainbowShell

Requirements:

  • Your program should print a prompt. At minimum, your prompt should show the current working directory and look distinct from the lab machine prompts. In other words, it should be easy to tell what shell if running from the terminal.

  • Use the readline() function to get user input. This function supports backspace, tab completion, and more. Documentation for readline can be found here.

  • Use the add_history() function to save user history. This will allow arrow keys to work. Documentation for readline can be found here.

  • Your program should quit if the users types exit.

  • When the user gives a command, split it into a command and arguments and then fork a command to execute it.

  • Your terminal should wait for the command to finish. If the command terminates with an error, report the error.

readline is a package that is installed on goldengate and in our labs. However, you may need to install it on your own machine. On Unix systems, this can be done by running sudo apt install libreadline-dev
You can print with colors to the console using ANSI escape sequences (see below). For example, printf(ANSI_COLOR_GREEN "Green Text" ANSI_COLOR_RESET); will print green text. Here is a good guide! 
// Helpful macros for working with color
#define ANSI_COLOR_RED     "\x1b[31m"
#define ANSI_COLOR_GREEN   "\x1b[32m"
#define ANSI_COLOR_YELLOW  "\x1b[33m"
#define ANSI_COLOR_BLUE    "\x1b[34m"
#define ANSI_COLOR_MAGENTA "\x1b[35m"
#define ANSI_COLOR_CYAN    "\x1b[36m"
#define ANSI_COLOR_RESET   "\x1b[0m"
Most prompts print helpful information. Above, we use the system commands gethostname, getcwd, and getpwuid(geteuid()) to get the machine name, the current working directory, and current user respectively.

3. Submit your work

Push your code to github to submit your work

$ git status
$ git add .
$ git status
$ git commit -m "assignment complete"
$ git status
$ git push
$ git status

4. Grading Rubric

Assignment rubrics

Grades are out of 4 points.

  • (2 points) Grep

    • (1.0 points) correct and complete behavior: reports found keywords, counts, and timing

    • (1.0 points) no memory errors, style

  • (2 points) Shell

    • (1.0 points) correct and complete behavior: runs commands, reports errors, shows prompt

    • (1.0 points) no memory errors, style

Code rubrics

For full credit, your C programs must be feature-complete, robust (e.g. run without memory errors or crashing) and have good style.

  • Some credit lost for missing features or bugs, depending on severity of error

  • -5% for style errors. See the class coding style here.

  • -50% for memory errors

  • -100% for failure to checkin work to Github

  • -100% for failure to compile on linux using make