ICS 54: Brief Notes on Chapter 6: File and Directory Basics

The UNIX file system is hierarchical

% pwd 
/home/ics54/www

  ./doc
  ./doc/Ch01
  ./doc/Ch02
  ......
  ./doc/Ch18
  ./doc/Ch18/Part1
  ./doc/Ch18/Part1/images
  ./doc/Ch18/Part2
  ......
  ./doc/apache
  ./doc/apache/Live
  ./doc/apache/Live/conf
  ./doc/apache/Live/conf/OLD
  ./doc/apache/Live/temp
  ./images
  ./images/OLD
  ./originals
  ./private
  ./private/doc

The UNIX file system's contents

• A directory is a (special) file containing
  names and addresses of other files
• A regular (ordinary) file contains data which might, in fact, be an executable program
• A symbolic link is a file which points to another file
• A hard link a directory entry giving a file an alternate name.
• Other collections, sources, or targets of data flow are also treated as special files:
  • Character and Block Device Files
  • UNIX Domain Sockets (BSD)
  • Named Pipes (ATT)

System directories

• /bin /user/bin: executables for many Unix commands
• /etc: system data files
• /dev: special files representing I/O devices
  • /dev/ttyp0: pseudo terminals
  • /dev/kmem: memory
  • /dev/printer: printer
  • /dev/null: the null device
• /usr/man: contains manual pages
• /tmp: for temporary files

Accessing files and directories

• Each user ($USER) has a home directory ($HOME)
• Specify a file in one of three ways
  • a simple file name
  • absolute/full path name
  • relative path name =
    path name relative to the current working directory
• $cwd = Current Working Directory
  • cd = Change Directory
  • . = the current working directory
  • .. = the parent of the current working directory
• Files whose names begin with "," or "#" are "scratch files" and deleted periodically