Exercise #1

1. Re-make for yourself up to 3 Unix commands, one (or more if you wish) from each group from the given list below. The system calls you will likely need to use are listed after the command you may re-make. "open(2)" means to read the online manual for open in section 2, i.e. use the command "man 2 open" at your prompt. Your commands may be relatively simple (i.e. cp only needs to copy a single file for example,) but the more complete the better. With no options, your program should print a usage message and terminate. Your programs should also print a more detailed help/manual if --help is given on the command line.

   Note that you will need to check for error conditions and print appropriate status messages. You may use perror(3) for this.

2. Create a Makefile that can compile all your programs.

Group one:

cp / cat / more:

• open(2)
  • open and possibly create a file
• close(2)
  • close a file descriptor
• read(2)
  • read from a file descriptor
• write(2)
  • write to a file descriptor

Group two:

ls / tree / du:

• stat(2), lstat(2)

  • get file status

• statx(2)

  • get file status (extended)

• Note there is no C wrapper to the readdir(2) system call, so if you want to read a directory of files, use: opendir(3)/readdir(3) or scandir(3) scandir(3) is probably easiest to use.

Group three:

mv:

• rename(2)
  • change the name or location of a file

link / ln:

• link(2)
  • make a new name for a file (hard link)
• symlink(2)
  • make a new name for a file (symbolic link)

rm / unlink:

• unlink(2)
  • delete a name and possibly the file it refers to

mkdir:

• mkdir(2)
  • create a directory

rmdir:

• rmdir(2)
  • delete a directory

chmod:

• chmod(2)
  • change permissions of a file

readlink:

• readlink(2)
  • read value of a symbolic link

kill:

• kill(2)
  • send signal to a process

touch:

• utime(2)
  • change file last access and modification times
• creat(2) / open(2)
  • open and possibly create a file

Group four:

stat:

• stat(2), lstat(2)
  • get file status
• statx(2)
  • get file status (extended)

uname:

• uname(2)
  • get name and information about current kernel

uptime / free:

• sysinfo(2)
  • return system information

df:

• statfs(2)
  • get filesystem statistics