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Unix training session 1


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UNIX Architecture
UNIX file system
Relative & Absolute path
File permission
Directory related commands
Files related commands
Miscellaneous commands

Published in: Technology
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Unix training session 1

  1. 1. Introduction  UNIX Architecture  UNIX file system  Relative & Absolute path  File permission  Directory related commands  Files related commands  Miscellaneous commands  Presented by – Anil Kumar Kapil February 7, 2014 UNIX
  2. 2. INTRODUCTION What is UNIX?         Available in different flavors       An operating system Invented in 1969 at AT&T Bell Labs Command Line Interpreter GUIs (Window systems) are now available Written in the C programming language. Multi-user : Several people can use a UNIX computer at the same time Multi-process : A user can also run multiple programs at the same time Solaris (Sun), AIX (IBM) Linux (open source) Irix (SGI) Berkeley Unix is case-sensitive. February 7, 2014 
  3. 3.  The UNIX operating system is made up of three parts; the kernel, the shell and the programs.   Commands and Utilities: There are various command and utilities which you would use in your day to day activities. cp, mv, cat and grep etc. Shell: Shell is an interface between user and kernel. Shell interprets your input as commands and pass them to kernel. Utilities and Programs User Interface Operating System Computer Hardware Unix Kernel  Kernel : The kernel is the heart of the operating system. It interacts with hardware and most of the tasks like memory management, task scheduling and file management . Shell (sh, bash, tcsh, ksh …) cp, cat, rm, mv, grep, find, ls etc… February 7, 2014 UNIX ARCHITECTURE
  4. 4. UNIX FILE SUBSYSTEM All data in UNIX is organized into files. All files are organized into directories. These directories are organized into a tree-like structure called the filesystem.  In UNIX, data, directory, process, hard disk etc (almost everything) are expressed as a file.  Basic Directory Terms Home directory The home directory is a directory assigned to a user. When you log in, your working directory will be set to your home directory Root directory Top of a file tree Current directory Directory you’re in now Dot (.) Another term for the current directory Dot-dot (..) Parent of the current directory Tilde (~) $HOME directory February 7, 2014 
  5. 5. UNIX FILE SUBSYSTEM February 7, 2014 NOTE: Unix file names are CASE SENSITIVE! Important Directories /bin This contains files that are essential for correct operation of the system. These are available for use by all users. /home  This is where user home directories are stored. /var This directory is used to store files which change frequently, and must be available to be written to. /etc  Various system configuration files are stored here /dev  This contains various devices as files, e.g. hard disk, CD- ROM drive, etc. /sbin  Binaries which are only expected to be used by the super user. /tmp Temporary files.
  6. 6. UNIX FILE SUBSYSTEM In UNIX there are three basic types of files:   Directory is a special file that contains the names of other files and/or subdirectories..   Regular file holds ASCII text, binary data, image data, databases, applicationrelated data, and more Symbolic link. A type of file that point to another file Every file has a data structure (record) known as an I-node that stores information about the file, and the filename is simply used as a reference to that data structure. February 7, 2014 
  7. 7. UNIX FILE TYPE Regular file : Most common file type found in the Solaris Operating Environment  Store different kinds of data.  Regular files can hold ASCII text, binary data, image data, databases, application-related data, and more.  February 7, 2014 
  8. 8. UNIX FILE TYPE Directory file : Directories store information that associates file names with inode numbers.  Unlike regular files that can hold many different kinds of data, directories can hold only one kind  February 7, 2014 
  9. 9. UNIX FILE TYPE Symbolic link : A symbolic link is a file that points to another file.  Like directories, symbolic links contain only one kind of data.  A symbolic link contains the pathname of the file to which it points.  February 7, 2014 
  10. 10. RELATIVE & ABSOLUTE PATH Path means a position in the directory tree.  Relative path    Absolute path    starts from current working directory If you are already in the users directory, the Relative pathname for file1 is usern/file1 start from root (/) and follow the tree The absolute pathname for file1 is /users/usern/file1 Specifying Paths   What is the absolute path to index.html? What is the relative path to index.html (assuming that usern is your pwd)? February 7, 2014 
  11. 11. LISTING FILES ls: To list the files and directories stored in the current directory. Syntax: ls [<file> … ]      ls - short listing ls -l - long listing ls -a  list all the files including hidden files that start with . . ls –lt  list all files names based on the time of creation, newer files bring first. ls –R lists all the files and files in the all the directories, recursively. Example: ls –l backup -rw-r--r-drwxr-xr-x lrwxr-xr-x  1 ian wheel 4 ian admin 1 ian admin 9218 136 16 21 17 6 Aug 14:49 Jan 16:31 Jan 19:31 support.dat talk-others w -> /shared/w In the ls -l listing example, every file line began with a d, -, or l. These characters indicate the type of file Prefix Description - Regular file, such as an ASCII text file, binary executable, or hard link. D Directory file that contains a listing of other files and directories. L Symbolic link file. Links on any regular file. February 7, 2014 
  12. 12. FILE PERMISSION  Suppose you type in ls -l and the result is Typesrwx r-x r--access supported22:28UNIX. of file 1 hans doc 858 Aug 22 by hw1 -    r – read only permission What do all these symbols mean? w –write permission x –execute permission   in case of directory, “x” grants permission to list directory contents. It signifies whether you are permitted to search files under the directory Unix users can be classified into these categories:    User – the user who created the file. Group – the group owns the file. Other – the rest of the world February 7, 2014 
  13. 13.  Chmod  Change the access mode of one or more files Symbolic mode    Whose (user, group, or others) permissions you want to change What (+ to add, - to subtract, = to equal) operation you want to perform on the permission The permission (r, w, x) Numeric modes Permissions are stored in the UNIX system in octal numbers. An octal number is stored in UNIX system using three bits  Bit 1, value 0 or 1 (read permission) , weight 4  Bit 2, value 0 or 1 (write permission), weight 2  Bit 3, value 0 or 1 (defines execute permission), weight 1 For example, a value of 101 will be 5. (The value of binary 101 is (4 * 1) + (0 * 1) + (1 * 1) = 5.) Examples:     umask: Each time a file is created, its initial file mode is defined by applying the current value of the file creation mask     chmod o+r file.txt chmod u+x file.txt chmod u=rwx, g=r, o=wr my_file umask  Show see the current value of the file creation mask umask 077  To change the value of the file creation mask chgrp: change group of the file chown: change owner of the file Examples  chmod 751 my_file -R recursively descend through directory changing group of all files and subdirectories February 7, 2014 FILE PERMISSION
  14. 14.  pwd: the absolute pathname of your current working directory  cd: Change directory Examples:  cd backups/unix-tutorial  cd ../class-notes  cd ~  cd .. February 7, 2014 WORKING WITH DIRECTORIES
  15. 15.  cat: Display the contents of file Syntax: cat <file> Examples:  cat /export/home/xyz.txt  cat displays a file with no page breaks  cat file1 file2 >file3  concatenates file1 and file2, and writes the results in file3. If no input file is given, cat reads from the standard input file.  cat /dev/null/ > message.log  To Cleanup a file content : # /dev/null/ acts as a black hole from where anything directed to or read from is set as Null.  more: displays a file one screenful at a time   more file1 cp: Copy file Syntax: cp [options] <sources> <destination> Options: -i Interactive. cp prompts for confirmation whenever the copy would overwrite an existing target. A Y answer means that the copy should proceed. Any other answer prevents cp from overwriting target. -r  Recursive. cp copies the directory and all its files, including any subdirectories and their files to target.  cp tutorials.txt tutorial.txt.bak  cp –r dir1 /export/home/bsarda/dir2  touch: update the access and modification times of given file touch a.txt -a - Changes the access time of file. -m Changes the modification time of file.  February 7, 2014 FILES RELATED COMMANDS
  16. 16.  rm: remove file Syntax: rm [options] <file> Examples:  rm tutorials.txt  rm -rf /export/home/anil/dir2/ --This will remove files (write-protected too becoz of –f option) recursively from the directory. If the dir is write-protected then it cant.  mv: Move/Rename file/directory Syntax: mv [options] <sources> <destination> Examples:  mv tutorials.txt tutorial2.txt  mv tutorials.txt /export/home/anil/dir2/  head: Showing first “n” lines of file, by default will display the first 10 lines of a file Syntax: head –n file1 Examples:  head -20 tutorials.txt  tail: Showing last “n” lines of file, by default will display the last 10 lines of a file Syntax: tail –n file1 Examples:  tail -20 tutorials.txt  wc: counts the characters, words or lines in a file depending upon the option.    wc -l filename  print total number of lines in a file. wc -w filename print total number of words in a file. wc -c filename  print total number of characters in a file.  diff: compare the two files and print out the differences  cmp: compare the two files and print out the differences February 7, 2014 FILES RELATED COMMANDS
  17. 17.   man: This is help command, and will explains you about online manual pages date: Display date and time date + “%m-%d-%y %H:%M:%S” date + “%D” -- mm/dd/yy  date + “%T” --hh:mi:ss To get year as 2009 in full use „Y‟ otherwise „y „will give 09 only. # To have a new line in between Date and Time use %n like $date “+Date : %D %n %T” will give the output as  Date: 09/19/08 09:29:28    banner: prints characters in a sort of ascii art poster  cal: print the calander on current month by default Examples:  banner wait Syntax: tail –n file1 Examples:  cal 8 1965  print calander of august of 1965  sleep Examples:  sleep 10  Tell a shell script to pause for 10 seconds   env: See environment variables  clear: clear the screen  dircmp: compares two directories. Example :If i have two directories in my home directory named dirone and dirtwo and each has 5-10 files in it. Then  dircmp dirone dirtwo will return this Dec 9 16:06 1997 dirone only and dirtwo only Page 1 ./cal.txt ./fourth.txt ./dohazaar.txt ./rmt.txt ./four.txt ./te.txt ./junk.txt ./third.txt February 7, 2014 MISCELLANEOUS COMMANDS
  18. 18. TEXT PROCESSING COMMANDS echo  sort: sort command sort the lines of a file or files, in alphabetical order Example:  sort file.txt  sort -r file.txt  sort –f file.txt  sort –n file.txt  sort -k3 file.txt  cut: selects a list of columns or fields from one or more files    -- display in reverse order -- ignore case -- numerical order -- Sorts using the third field of each line cut –d „ „ -f 1,2,11, 15-20 file.txt cut –c 1-8 file.txt  it will extract first 8 characters of every line in the file. uniq: removes duplicate adjacent lines from sorted file while sending one copy of each second file Examples  sort names | uniq -d  will show which lines appear more than once in names file Options: -c print each line once, counting instances of each. -d print duplicate lines once, but no unique lines.  -u print only unique lines    tee: Put output on screen and append to file Examples  who | tee -a > <file> February 7, 2014 
  19. 19. VIEWING & SETTING ENVIRONMENT VARIABLES env  PATH Variable   Which   List of places (directories) on the system where the shell should look to locate a command. Each command you type is physically located as a file somewhere on your file system To find whether a particular command exists in you search path. If it does exist, which tells directory contains that command Where February 7, 2014 
  20. 20. February 7, 2014 QUESTIONS ?
  21. 21. February 7, 2014 Thank You ……