CS 3733 Operating Systems, Fall 2006 Assignment 3 Comments

This assignment was graded on a basis of 30 points.

• strncpy does not always produce a string.
• r_read may do a partial read.
• for get_regular_files the result must be able to be freed with freemakeargv.
  This means that all of the strings containing the filename must be made with a single malloc.
  A simple way to do this is make a first pass and count the total length of all regular file names, malloc space a buffer, then make a second pass, filling the names in the buffer. Use makeargv to create the argument list.
• In get_regular_files you must create a string containing the path of each file you are testing, or you must chdir to the directory containing the files.
• get_file: you should choose appropriate flags when you open the file. You should use O_CREAT and probabaly O_TRUNC.
• get_file must close the file.
• send_file must first send the size of the file. Determine the size of the file using stat.
• In send_file do not try to make a buffer to hold the entire file. What would you do if the file were 1 Gig?
• Remember that read(fd,buf,n) (or r_read) will not necessarily read n bytes, even if you are reading from a file and the file has n bytes left to read.
• Remember that write(fd,buf,n> will not necessarily write n bytes. Use r_write.
• C declarations must be at the start of a block.
• No printing from anything in list_utility.c. This means do not use perror.
• Use char buf[65] instead of malloc.
• Watch out for memory leaks.
• What does the following do:
     sprintf(buf, "%d\0");
• It is useful to understand the general goal of the assignment. This will help you understand why you are writing the functions.

• It should be clear from your test output what you tested and whether it gave the correct answers.
• Example: To test get_regular_files, show the result of ls -la on the directory and then show the regular files found. Make sure you do this int a directory with subdirectories and FIFOs.
  Don't just test this on the current directory. This is a special case.
• Example: To test send_integer write a main program that sends a integer to a FIFO. In another window, redirect the output of the FIFO to a file. State what the integer the main program sent, and show the contents of the file.
• You can test get_file in a similar way with a main program that gets the file from a FIFO. In another window, send a file to the FIFO. compare the resulting files.
• You can test send_file in a similar way. Or you can have one program doing a get_file and the other a send_file and connect these together with a FIFO. Compare the resulting files.

What is wrong with the following:

char * makepath(char *dir, char *name) {
   int length = strlen(dir) + strlen(name) + 2;
   char temp[length];
   strcpy(temp,dir);
   strcat(temp,"/");
   strcat(temp,name);
   return temp;
}