Remember the different Linux manual sections.
man 1  ->  user commands
man 2  ->  Linux system calls
man 3  ->  C library functions (but not necessarily C Standard Library functions)
man 4  ->  special files
man 5  ->  file formats
man 8  ->  administration and privileged commands

Note: These are the current manual sections. Our textbook uses an
older numbering for manual sections. For example, the book considers
Section 4 to be file formats, but that is now Section 5.

You can get an introduction to section n with the command
$ man n intro

--------------------------------------------------------------------------
Section 4.2

Read about the -R option to ls.
man 1 ls

--------------------------------------------------------------------------
Section 4.3

Read about the -i option to ls.
man 1 ls

dirent.h
/usr/include/dirent.h
/usr/include/bits/dirent.h

struct dirent
{
  __ino64_t        d_ino;
  unsigned char    d_type;
  unsigned char  __d_unused1[3];
  __uint32_t     __d_internal1;
  char             d_name[NAME_MAX + 1];
};

--------------------------------------------------------------------------
Section 4.4

man 1 mkdir
man 2 mkdir

man 1 rmdir
man 2 rmdir

man 1 rm
man 1 unlink
man 2 unlink

man 1 ln
man 2 link

man 1 mv
man 1 rename
man 2 rename

cd
man 2 chdir

--------------------------------------------------------------------------
Section 4.5

The real version of the command pwd is written in terms of the system call getcwd().

man 1 pwd
man 3 getcwd


--------------------------------------------------------------------------
Section 4.6

man 1 mountpoint
man 8 mount
man 2 mount


man 1 ln -s
man 7 symlink
man 2 symlink
man 2 readlink
man 2 lstat