1 Introduction to Unix

2 What is UNIX?  UNIX is an Operating System (OS).  An operating system is a control program that helps the user communicate with the computer hardware.  UNIX was developed long before Windows, about 30 years ago at AT&T Bell Labs in the US (95% written in “C” programming language).

3 What is UNIX?  Designed as an operating system for experts, used on high-end workstations, servers and hosts.  UNIX provides some powerful features: Security, Multi-user support, Inter-process communication, Extensive network support  Windows NT was developed by Microsoft to try to replace UNIX as the “OS for experts”.

4 Getting Started with UNIX  You can access these computers with putty from other computers via the vpn: ubunix.cc.buffalo.edu  You need to log in to a UNIX computer with a valid account and password: login: zelli Password:

5 Basic UNIX File Utilities  ls list files in current directory  cat display (concatenate) file  more display one screen of file  rm remove (delete) a file  cp copy source file to target file  mv rename or move a file  lpr print a file  man online UNIX help manual

6 Utilities for Finding Info  who who is logged on where and when  finger additional login information  date print the date and time  cal displays a calendar  head display the first few lines of file  tail display the last few lines of file  weather current weather forecast  quota -v displays user’s disk quota

7 Unix Filesystem  The filesystem is a hierarchical system of organizing files and directories.  The top level in the hierarchy is called the "root" and holds all files and directories.  The name of the root directory is /

8 Directory Shorthands  “.” is the directory itself  “..” is the parent directory  “~” indicates your home directory  ~user means user’s home directory, so: > more ~zelli/.plan  looks at the file.plan in /home/zelli, which is zelli’s home directory.

9 Some things to try ls list files in current directory ls / list files in the root directory ls. list files in the current directory ls.. list files in the parent directory ls /usr list files in the directory /usr

10 Directory Commands  pwd shows current directory  cd changes to another directory  mkdir creates a directory  rmdir removes a directory  mv move a file or directory elsewhere  ls list files in a directory

11  Use ls -l to view file permissions  There are four sets of items in the permissions: -rw-r--r-- The type is: “-” regular files, “d” directories, “l” symbolic links. The next nine characters indicate if the file is readable, writable, or executable for the file owner, the file group, or other users, respectively. Security and Permissions

12 Security and Permissions  There are three types of users: The owner of the file (user) The group of the file (group) Anyone else (other)  There are three types of permission (independent of each other): Read, Write and Execute

13 Changing Permissions  The chmod command is used to modify permissions.  chmod can only be used by the owner of a file/dir (or the administrator root).  The arguments are: chmod [ugoa] [+-=] [rwxdd] [file/dir]

14 Changing Permissions  Another way to change permission is to use numbers representing the permissions. Code table (3 bits) r x 1 r-x5 -w- 2 rw-6 -wx 3 rwx7

15 Other Useful Programs  pine program used to read  lynx text based web browser  ftp FTP program  nano user friendly text editor  vi another text editor  emacs even another text editor