Basic Unix

UNIX Basics www.scmGalaxy.com Author: Rajesh Kumar www.scmGalaxy.com, Author - Rajesh Kumar

Contents 1.Introduction to Unix 03 - 11 2. Logging In and Basic Commands 12 - 26 3File system 27 - 45 4.managing files 46 - 55 5.File Access Permissions 56 - 68 6.vi Editor 69 - 78 7.Shell Basics 79 – 94 8. Standard I/O Redirection 95 – 103 9. Filters & some utilities 104 – 123 10. Controlling Processes 124 – 132 11. Shell Programming concepts 133 - 158 12. Labs 159 - 161 www.scmGalaxy.com, Author - Rajesh Kumar

Introduction to Unix Module 1 www.scmGalaxy.com, Author - Rajesh Kumar

Objectives Upon completing this module you should be able to understand the following: what is an Operating System History of unix Operating system Unix Architecture More features of unix Unix Flavors Linux Flavors www.scmGalaxy.com, Author - Rajesh Kumar

What Is an Operating System? Interface between Users and the Hardware take care of Storage Management take care of I/O device management www.scmGalaxy.com, Author - Rajesh Kumar

1969 AT&T Bell Labs UNICS system -designed by Ken Thompson & Dennis Ritchie 1970 UNICS finally became UNIX 1973 UNIX rewritten in C, making it portable to different hardware Mid 1970s University of California at Berkeley (BSD) contributed many important features like vi, C shell etc. 1982 AT & T came back and started commercial production- Editions ->Systems Late 1980s AT & T released SVR4 unification of SV3.2,BSD,SunOs & XENIX 1991 Linux from Linus Torvalds 1990s POSIX Standard, MIT introduced X-Windows History of the UNIX Operating System www.scmGalaxy.com, Author - Rajesh Kumar

UNIX Architecture – Kernel & Shell Shell Kernel Hardware User www.scmGalaxy.com, Author - Rajesh Kumar

UNIX Architecture – System Calls Though there are over a thousand commands on the system, they all use a handful of functions, called system calls, to communicate with the kernel. All unix flavors use the same system calls and are described in the POSIX specification. www.scmGalaxy.com, Author - Rajesh Kumar

Hierarchical file system Multi tasking Multi user The building block approach Pattern matching (wildcard characters) Toolkit(Applications, RDBMSs, Languages etc..) Programming facility Documentation More Features of UNIX www.scmGalaxy.com, Author - Rajesh Kumar

Flavors of UNIX Digital Unix IRIX SCO Open Server SCO UnixWare IBM -AIX HP - UX Sun - Solaris www.scmGalaxy.com, Author - Rajesh Kumar

Clone of UNIX (LINUX) Red Hat Calders SuSE Mandrake Debian www.scmGalaxy.com, Author - Rajesh Kumar

Logging In and Basic Commands Module 2 www.scmGalaxy.com, Author - Rajesh Kumar

Objectives Upon completing this module you should be able to understand the following: Logging In and Out Command Line Format The Secondary Prompt Online Manual Pages id Command who Command date Command cal, clear Commands passwd Command finger command www.scmGalaxy.com, Author - Rajesh Kumar

Log in to identify yourself and gain access. Execute commands to do work. Log off to terminate your connection. A Typical Terminal Session www.scmGalaxy.com, Author - Rajesh Kumar

Logging In and Out telnet 192.168.10.1 User: Password: exit or <ctrl>+<d> will terminate the login session www.scmGalaxy.com, Author - Rajesh Kumar

Syntax: $ command [- options] [arguments] Separation : mail –f newmail not mail – f newmail Order: mail –f newmail not mal newmail –f Multiple options: who –m –u or who –mu not who –m u Multiple arguments: mail team1 team2 not mail team1team2 Command Line Format www.scmGalaxy.com, Author - Rajesh Kumar

$ echo 'hi >Good Morning‘ > is the default secondary prompt The Secondary Prompt www.scmGalaxy.com, Author - Rajesh Kumar

Content of the Manual Pages NAME WARNINGS SYNOPSIS EXAMPLES DESCRIPTION AUTHOR RETURN VALUE FILES ERRORS SEE ALSO BUGS etc. www.scmGalaxy.com, Author - Rajesh Kumar

Syntax: man –[k|X] keyword in which X is the number of one of the manual sections Examples: $ man ls Display the “ls" man page. $ man -k cat Display entries with keyword "cat". $ man passwd Display the "passwd" man page-Section 1. $ man 4 passwd Display the "passwd" man page-Section 4. The Online Manual www.scmGalaxy.com, Author - Rajesh Kumar

Syntax: id Displays effective user and group identification for session Example: $id uid =303 (user3) gid=300 (class) The id Command www.scmGalaxy.com, Author - Rajesh Kumar

Syntax : who Reports information about users who are currently logged on to a system Examples: $ who root tty1p5 Jul 01 08:01 user11 tty1p4 Jul 01 09:59 user12 tty0p3 Jul 01 10:01 $ who am i user12 tty0p3 Jul 01 10:01 $ whoami user12 The who Command www.scmGalaxy.com, Author - Rajesh Kumar

Syntax: date Reports the date and time Example: $ date Fri Jul 1 11:15:55 EDT 2005 The date Command www.scmGalaxy.com, Author - Rajesh Kumar

Syntax: cal Reports the calendar of 2005 September(Current month) Example: $ cal 8 2005 for Aug 2005 $ cal 2005 for the full calendar of year 2005 The cal Command www.scmGalaxy.com, Author - Rajesh Kumar

Syntax: passwd Assigns a login password Example: $ passwd Changing password for user1 Old password: New password: Re-enter new password: The passwd Command www.scmGalaxy.com, Author - Rajesh Kumar

The clear Command Syntax: clear Clears terminal screen www.scmGalaxy.com, Author - Rajesh Kumar

finger Finger: Displays information about the users currently logged on Eg: $ finger user1 Login name: user1 Directory: /export/home/user1 shell:/usr/bin/sh On since Sep 05 09:10:12 on tty1 No plan www.scmGalaxy.com, Author - Rajesh Kumar

File System Module 3 www.scmGalaxy.com, Author - Rajesh Kumar

Objectives Upon completing this module you should be able to understand the following: What Is a File System? File System structure Hard Link File Types Ordinary Files Directory Files Symbolic Links Device files The File System Hierarchy Basic Commands pwd, cd, ls, mkdir, rmdir, touch www.scmGalaxy.com, Author - Rajesh Kumar

What Is a File System? collection of control structures and Data blocks that occupy the space defined by a partition and allow for the storage and management of data. Data + Meta data www.scmGalaxy.com, Author - Rajesh Kumar

a File System structure www.scmGalaxy.com, Author - Rajesh Kumar Primary Superblock Backup Superblock Cylinder Group Block Inode Table Data Blocks

Hard Link Allows a file to have more than one name and yet maintain a single copy on the disk. All the links have the same inode number Eg: $ ls –i f1 1113 f1 $ ln f1 f1.lnk $ ls –i f1.lnk 1113 f1.lnk www.scmGalaxy.com, Author - Rajesh Kumar

a File Types Common File Types: Ordinary files: regular files Directory files: table of contents, that stores a list of files/directories within that directory Device files: For every device there is a device file used by kernel to interact with the device. Symbolic Link: Its link to other files www.scmGalaxy.com, Author - Rajesh Kumar

a Ordinary Files A regular file simply holds data. Regular files can hold ASCII text, binary data, image data, databases, application-related data, and more. www.scmGalaxy.com, Author - Rajesh Kumar

a Directory Files Directory Inode Table name inum # type mode links user group date size loc d1 4 4 dir 755 2 user1 group1 Sep 5 9:30 512 f1 10 10 file 644 1 user1 group1 Sep 5 9:45 12 www.scmGalaxy.com, Author - Rajesh Kumar

a Symbolic Links contains the path of the file to which it links Exists even after the source file is removed and is exactly similar to Windows shortcut Syntax: ln –s soucefile linkfile Eg: ln -s /f1 f1.lnk Overcomes 2 limitations of Hard Link: 1. possible across filesystems 2. can link to a directory www.scmGalaxy.com, Author - Rajesh Kumar

a Device files A device file provides access to a device. # cd /devices/pci@1f,0/pci@1,1/ide@3 # ls -l brw------- 1 root sys 136, 0 Apr 3 11:11 dad@0,0:a Two types of device files: block device files character device file www.scmGalaxy.com, Author - Rajesh Kumar

The File System Hierarchy / usr etc devices dev var tmp bin sbin ls who adm sadm dsk rdsk www.scmGalaxy.com, Author - Rajesh Kumar

a system directories / :root directory, top level directory /bin : user commands like cp, cron, cmp etc.. /usr/sbin: admin commands /dev : logical device files of all hardware devices /devices: physical device files /etc : System configuration files and user database /tmp : to store temporary files /usr : the binaries, shared libraries, shared documentation etc. /var: stores the log files and dynamic files www.scmGalaxy.com, Author - Rajesh Kumar

a File Path name A sequence of file names, separated by slashes (/), that describes the path, the system must follow to locate a file in the file system Absolute pathname (start from the /-directory): Eg: /export/home/user1/file1 Relative pathname (start from the current directory) ./test1 (. = current directory) ../team03/.profile (.. = parent directory) www.scmGalaxy.com, Author - Rajesh Kumar

pwd - Present Working Directory pwd prints the Current Directory www.scmGalaxy.com, Author - Rajesh Kumar

6 Syntax: ls [-adlFR] [ pathname(s)] Example: $ ls f1 f2 memo $ ls -F f1 f2* memo/ $ ls -aF profile f1 f2* memo/ $ ls memo f1 f2 ls - List Contents of a Directory www.scmGalaxy.com, Author - Rajesh Kumar

cd Change Directory Example: $ pwd /home/user3 $ cd memo; pwd / home/user3/memo $ cd ../..; pwd /home $ cd /tmp; pwd /tmp syntax: cd [dir_name] www.scmGalaxy.com, Author - Rajesh Kumar

mkdir, rmdir – create & remove Directories Syntax: mkdir directory eg: $ mkdir d1 syntax: rmdir dir eg: $ rmdir /export/home/user1 www.scmGalaxy.com, Author - Rajesh Kumar

working with Multiple Directories Create multiple directories simultaneously: $ mkdir -p dir1/dir2/dir3 Remove a directory and all its subdirectories $ rmdir -p dir1/dir2/dir3 www.scmGalaxy.com, Author - Rajesh Kumar

The touch Command Updates the atime and mtime of a file if it exists. Else create an empty file Example: $ ls –l -rw-r—r-- 1 user1 group1 100 Sep 5 09:30 test $date Mon, Sep 5 10:00 2005 $ touch test file1 $ ls -l -rw-r—r-- 1 user1 group1 100 Sep 5 10:00 test -rw-r—r-- 1 user1 group1 100 Sep 5 10:00 file1 www.scmGalaxy.com, Author - Rajesh Kumar

Managing Files Module 4 www.scmGalaxy.com, Author - Rajesh Kumar

Objectives Upon completing this module you should be able to understand the following: File Characteristics cat more tail wc cp mv rm www.scmGalaxy.com, Author - Rajesh Kumar

File Characteristics File Type Permissions Links Owner Group Size Timestamp Name $ ls -l -rw-r--r-- 1 user3 class 37 Jul 24 11:06 f1 -rwxr-xr-x 1 user3 class 52 Jul 24 11:08 f2 drwxr-xr-x 2 user3 class 1024 Jul 24 12:03 memo www.scmGalaxy.com, Author - Rajesh Kumar

Syntax: cat [ file...] Concatenate and display the contents of file(s) Examples: $ cat remind Your mother's birthday is November 29. $ cat note remind The meeting is scheduled for July 29. Your mother's birthday is November 29. $ cat abc abc 1234 1234 cat - Display the Contents of a File www.scmGalaxy.com, Author - Rajesh Kumar CTRL + D

Syntax: more [ filename]... Display files one screen at a time Example: $ more funfile . . . --funfile (20%)-- Q or q Quit more Return One more line Space bar One more page more - Display the Contents of a File www.scmGalaxy.com, Author - Rajesh Kumar

Syntax: tail [- n] [filename]... Display the end of file(s) Example: $ tail -1 test soon as it is available. tail - Display the End of a File www.scmGalaxy.com, Author - Rajesh Kumar

wc command The wc command counts the number of lines, words and bytes in a named file: syntax: wc [-c] [-l] [-w] filename Options: -c counts the number of bytes -l counts lines -w counts words Example: $wc testfile 10 98 1000 testfile www.scmGalaxy.com, Author - Rajesh Kumar

Syntax: cp [-i] file1 new_file Copy a file cp [-i] file [file...] dest_dir Copy files to a directory cp -r [-i] dir [dir...] dest_dir Copy directories Example: cp file1 d1 copies file1 to d1 directory cp file2 file3 create a copy of file2 as file3 in the same directory cp - Copy Files www.scmGalaxy.com, Author - Rajesh Kumar

Syntax: mv [-i] file new_file Rename a file mv [-i] file [file...] dest_dir Move files to a directory mv [-i] dir [dir...] dest_dir Rename or move directories Example: $ ls -F $ mv note remind memo f1 f2* memo/ note remind $ ls -F $ mv f1 file1 file1 memo/ $ ls -F $ls -F memo file1 f2* memo/ note remind file2* note remind $ mv f2 memo/file2 $ mv memo letters $ ls -F $ ls -F file1 memo/ note remind file1 letters/ $ ls -F memo file2* mv - Move or Rename Files www.scmGalaxy.com, Author - Rajesh Kumar

Syntax: rm [-if] filename [filename...] Remove files rm -r[if] dirname [filename...] Remove directories Examples: rm f1 removes the file f1 rm –r d1 remove the directory. rm - Remove Files www.scmGalaxy.com, Author - Rajesh Kumar

File Access Permissions Module 5 www.scmGalaxy.com, Author - Rajesh Kumar

Objectives Access to files is dependent on a user's identification and the permissions associated with a file. This module will show how to Understand the read, write, and execute access to a file Permissions ls (11, ls -l) chmod umask chown chgrp su setuid, setgid, sticky bit www.scmGalaxy.com, Author - Rajesh Kumar

File Permissions and Access Access to files is dependent on a user's identification and the permissions associated with a file. This module will show how to Understand the read, write, and execute access to a file Permissions ls (11, ls -l) chmod umask chown chgrp su Determine what access is granted on a file Change the file access Change default file access Change the owner of a file Change the group of a file Switch your user identifier www.scmGalaxy.com, Author - Rajesh Kumar

Who can access a File? The UNIX system incorporates a three-tier structure to define who has access to each file and directory: user The owner of the file group A group that may have access to the file other Everyone else The ls -l command displays the owner and group who has access to the file. $ ls -l -rw-r--r-- 1 user3 class 37 Jul 24 11:06 f1 -rwxr-xr-x 1 user3 class 37 Jul 24 11:08 f2 drwxr-xr-x 2 user3 class 1024 Jul 24 12:03 memo | | owner group www.scmGalaxy.com, Author - Rajesh Kumar

contents can be examined. contents can be examined. contents can be changed. contents can be changed. file can be used as a command. can become current working directory. Types of Access There are three types of access for each file and directory: Read files: directories: Write files: directories: Execute files: directories: www.scmGalaxy.com, Author - Rajesh Kumar

Change Permissions (Symbolic Notation) Syntax: chmod mode_list file... Change permissions of file(s) mode_list [who[operator]permission] [ ,... ] who user, group, other or all(u/g/a) operator + (add), - (subtract), = (set equal to) permission read, write, execute Example: Original permissions: mode user group other rw-r--r-- rw- r-- r-- $ chmod u+x,g+x,o+x file or $ chmod +x file Final permissions: mode user group other rwxr-xr-x rwx r-x r-x www.scmGalaxy.com, Author - Rajesh Kumar

Change Permissions(Octal Notation) File and directory permissions can also be specified as an octal number: Read Permission :4 Write Permission :2 Execute Permission:1 We can just add the numbers to specify the permission for each category Example: 6 means read and write, 7 means read, write and execute eg: $ chmod 664 f1 will give read and write permissions for owner and group while only read for others www.scmGalaxy.com, Author - Rajesh Kumar

Default Permissions The default protections for newly created files and directories are: File -rw-r—r-- 644 Directory drwxr-xr-x 755 These default settings may be modified by changing the umask value. www.scmGalaxy.com, Author - Rajesh Kumar

umask - Permission Mask Umask specifies what permission bits will be set on a new file or directory when created. New Directory: 777 – 022 755  rwxr-xr-x New File : 666 – 022 644  rw-r—r— The default value of umask is set in /etc/profile. This can be changed for all the users or a particular user www.scmGalaxy.com, Author - Rajesh Kumar

chown - Change File Ownership Syntax: chown owner [:group] filename ... Example: $ id uid=101 (user1), gid=101 (group1) $ cp f1 /tmp/user2/f1 $ ls -l /tmp/user2/f1 -rw-r----- 1 user1 group1 3967 Jan 24 13:13 f1 $ chown user2 /tmp/user2/f1 $ ls -l /tmp/user2/f1 -rw-r----- 1 user2 class 3967 Jan 24 13:13 f1 Only the owner of a file (or root) can change the ownership of the file. Changes owner of a file(s) and, optionally, the group ID www.scmGalaxy.com, Author - Rajesh Kumar

The chgrp Command Syntax: chgrp newgroup filename ... Example: $ id uid=303 (user3), gid=300 (class) $ ls -l f3 -rw-r----- 1 user3 class 3967 Jan 24 13:13 f3 $ chgrp class2 f3 $ ls -l f3 -rw-r----- 1 user3 class2 3967 Jan 24 13:13 f3 $ chown user2 f3 $ ls -l f3 -rw-r----- 1 user2 class2 3967 Jan 24 13:13 f3 www.scmGalaxy.com, Author - Rajesh Kumar

su - Switch User Id Syntax: su [ user_name] Example: $ ls -l f1 -rwxr-x--- 1 user1 group1 3967 Jan 24 23:13 class_setup $ id uid=303 (user1), gid=300 (group1) $ su – user2 Password: $ id uid=400 (user2), gid=300 (group1) Change your effective user ID and group ID www.scmGalaxy.com, Author - Rajesh Kumar

Special File Permissions – setuid, setgid, sticky bit setuid – changes the effective user id of the user to the owner of the program chmod u+s f1 or – chmod 4744 f1 setgid – changes the effective group id of the user to the group of the program chmod g+s f1 or chmod 2744 f1 sticky bit – ensures the deletion of files by only file owner in a public writable directory chmod +t f1 or Chmod 1744 f1 www.scmGalaxy.com, Author - Rajesh Kumar

vi Editor Module 6 www.scmGalaxy.com, Author - Rajesh Kumar

Objectives Upon completing this module you should be able to understand the following: What Is vi? Starting and Ending a vi Session Cursor Control Commands Input Mode: i, a, O, o Deleting Text: x, dw, dd, dG Copying, moving and changing Text Searching for Text: /, n, N Find and Replace www.scmGalaxy.com, Author - Rajesh Kumar

A screen-oriented text editor Included with most UNIX system distributions Command driven Categories of commands include General administration Cursor movement Insert text Delete text Paste text Modify text What Is vi? www.scmGalaxy.com, Author - Rajesh Kumar

Starting and Ending a vi Session vi [filename] Start a vi edit session of file Example: $ vi testfile - If the file doesn’t exist, it will be created - Otherwise vi will open the existing file All modifications are made to the copy of the file brought into memory. :wq or :x or <shift-zz> write and quit :w write :q quit :q! Quit without saving www.scmGalaxy.com, Author - Rajesh Kumar

Cursor Control Commands $ w,W l <right-arrow> <down-arrow> j L <ctrl-f> G 1G <ctrl-b> H k <up-arrow> 0 b,B h <left-arrow> www.scmGalaxy.com, Author - Rajesh Kumar

Input Mode: i, a, O, o i will insert character at the present cursor position I will insert character at the beginning of the line a will append character at the present cursor position A will append character at the end of the line o will insert a blank line below O will insert a blank line above www.scmGalaxy.com, Author - Rajesh Kumar

Deleting Text: x, dw, dd, dG x deletes the current character dw deletes the current word dd deletes the current line dG delete all lines to end of file, including current line. With any of these you can prefix a number Example: 3dd will delete 3 lines d$ to delete to the end of the line d0 to delete to the start of the line www.scmGalaxy.com, Author - Rajesh Kumar

Copying, moving and changing Text yy copy the line yw copy the word p will paste the yanked lines below dw cut the word P will paste the yanked lines above dd cut the line r will overwrite the current character R will replace all text on the right of the cursor position cw will replace only the current word www.scmGalaxy.com, Author - Rajesh Kumar

Searching for Text: /, n, N /director will locate for the first occurrence of the pattern ‘director’ n to locate the next occurrence N to locate the previous occurence www.scmGalaxy.com, Author - Rajesh Kumar

Find and Replace To find and replace the word director with member : : 1,$s/director/member/g 1,$ represents all lines in the file g makes it truly global. g will ensure that all occuences in each line is replaced. Without g only the first occurrence of each line will be replaced. www.scmGalaxy.com, Author - Rajesh Kumar

Shell Features Module 7 www.scmGalaxy.com, Author - Rajesh Kumar

Objectives Upon completing this module you should be able to understand the following: Shell functionalities Commonly Used Shells BASH Shell Features Aliasing, Command History Re-entering Commands The User Environment Setting Shell Variables Variable Substitution Command Substitution Transferring Local Variables to the Environment Functions of a Shell before Command execution. www.scmGalaxy.com, Author - Rajesh Kumar

Shell functionalities command execution environment settings variable assignment variable substitution command substitution filename generation I/O redirection Interpretive programming language www.scmGalaxy.com, Author - Rajesh Kumar

/bin/bash /bin/ksh /bin/sh /bin/csh /bin/rksh /bin/rsh /bin/tcsh /bin/zsh Bash shell Korn shell Bourne shell C Shell Restricted Korn shell Restricted Bourne shell An amended version of the C shell The Z shell Commonly Used Shells www.scmGalaxy.com, Author - Rajesh Kumar

A shell user interface with some advanced features: Command aliasing File name completion Command history mechanism Command line recall and editing Job control Enhanced cd capabilities Advanced programming capabilities BASH Shell Features www.scmGalaxy.com, Author - Rajesh Kumar

Syntax: alias [ name[=string]] Examples: $ alias dir=ls $ alias mroe=more $ alias mstat=/home/tricia/projects/micron/status $ alias laser="lp -dlaser" $ laser fileX request id is laser-234 (1 file) $ alias displays aliases currently defined $ alias mroe displays value of alias mroe mroe=more Aliasing www.scmGalaxy.com, Author - Rajesh Kumar

The shell keeps a history file of commands that you enter. The history command displays the last 16 commands. You can recall, edit, and re-enter commands previously entered. Syntax: history [- n| a z] Display the command history. Example: $ history -2 list the last two commands 15 cd 16 more .profile $ history 3 5 list command numbers 3 through 5 3 date 4 pwd 5 ls Command History www.scmGalaxy.com, Author - Rajesh Kumar

Example: $ history 3 5 list command numbers 3 through 5 3 date 4 pwd 5 ls $ r 4 run command number 4 pwd /home/kelley Re-entering Commands You type r c to re-enter command number c . www.scmGalaxy.com, Author - Rajesh Kumar

Syntax: env Example: $ env HOME=/home/gerry PWD=/home/gerry/develop/basics ... PATH=/usr/bin:/usr/contrib/bin:/usr/local/bin:\ /home/gerry/bin The User Environment Your environment describes your session to the programs you run. www.scmGalaxy.com, Author - Rajesh Kumar

The PATH variable A list of directories where the shell will search for the commands you type The TERM variable Describes your terminal type and screen size to the programs you run $ env ... PATH=/usr/bin:/usr/contrib/bin:/usr/local/bin $ TERM=70092 Two Important Variables www.scmGalaxy.com, Author - Rajesh Kumar

. Setting Shell Variables . . . Syntax: name=value Example: color=blue PATH=$PATH:/usr/ucb www.scmGalaxy.com, Author - Rajesh Kumar

$ echo $PATH /usr/bin:/usr/contrib/bin:/usr/local/bin $ PATH=$PATH:$HOME:. $ echo $PATH /usr/bin:/usr/contrib/bin:/usr/local/bin:/home/user3:. $ echo $HOME /home/user3 $ file_name=$HOME/file1 $ more $file_name <contents of /home/user3/file1> Variable Substitution www.scmGalaxy.com, Author - Rajesh Kumar

Syntax: $( command) Example: $ dt=date This will store the string date in the variable dt not the value $ dt=$(date) This will do command substitution and store the result of date command in the variable dt note: instead of $(date) we can also use `date` Command Substitution www.scmGalaxy.com, Author - Rajesh Kumar

. $ echo $HOME /home/user3 $ env HOME=/home/user3 … . SHELL=/usr/bin/sh $ set HOME=/home/user3 PATH=/usr/bin:/usr/contrib/bin:/usr/local/bin … . color=lavender count=3 dir_name=/home/user3/tree $ unset dir_name Displaying Variable Values www.scmGalaxy.com, Author - Rajesh Kumar

Transferring Local Variables to the Environment Syntax: export variable Transfer variable to environment www.scmGalaxy.com, Author - Rajesh Kumar

Functions of a Shell before Command execution. Searches for a command Substitutes Shell variable values. Command substitution, I/O redirection Interpreted programming interface www.scmGalaxy.com, Author - Rajesh Kumar

Standard I/O Redirection Module 8 www.scmGalaxy.com, Author - Rajesh Kumar

Objectives Upon completing this module you should be able to understand the following: The Standard Files Input Redirection Output Redirection Creating a file with cat Error Redirection Combined Redirection Split Outputs www.scmGalaxy.com, Author - Rajesh Kumar

The Standard Files Standard Input File (0) Keyboard Standard Output File (1) Monitor Standard Error File (2) Monitor operators: standard input redirection 0< or < standard output redirection 1> or > standard Error redirection 2> www.scmGalaxy.com, Author - Rajesh Kumar

Input Redirection Default standard input $ mail user1 subject: Hi Test mail <ctrl-d> Redirect Input from a file: < $ mail user1 < letter www.scmGalaxy.com, Author - Rajesh Kumar

Output Redirection Default standard output: $ ls f1 f2 f3 Redirect output from a file: > $ ls > ls.out Redirecting and appending output to a file: >> $ who >> who.out www.scmGalaxy.com, Author - Rajesh Kumar

Creating a file with cat While normally used to list the contents of files, using cat with redirection can be used to create a file $ ls file1 file2 file3 Using redirection $ cat > newfile file created by using the output redirection <ctrl-d> $ ls file1 file2 file3 newfile www.scmGalaxy.com, Author - Rajesh Kumar

Error Redirection Default standard error: $ cat file1 file3 This is file1 cat: cannot open file2 Redirecting error output to a file: 2> (To append: 2>>) $ cat file1 file3 2>err This is file1 $ cat err cat: cannot open file2 $ cat file1 file3 2> /dev/null www.scmGalaxy.com, Author - Rajesh Kumar

Combined Redirection Combined redirects: $ command > outfile 2>errfile <infile $ command >> appendfile 2 >> errorfile <infile Association Examples: $ command > outfile 2 >&1 note: This is NOT the same as above $ command 2>&1 >outfile www.scmGalaxy.com, Author - Rajesh Kumar

Split Outputs The tee command reads standard input and sends the data to both standard output and a file. Example: $ ls | tee ls.save | wc –l www.scmGalaxy.com, Author - Rajesh Kumar

Module 9 Filters & other commands www.scmGalaxy.com, Author - Rajesh Kumar

Objectives Upon completing this module you should be able to understand the following: grep, sort, find ,cut , tr ftp paste command split command uniq command diff(Differential file comparator) Command cmp command file command tar (tape archive program) Restoring Files www.scmGalaxy.com, Author - Rajesh Kumar

grep Search for lines matching specified pattern syntax: grep [options] pattern [file1 file2 …..] Example: emp.dat Robin Bangalore John Chennai Rina Bangalore $ grep Bangalore emp.dat Robin Bangalore Rina Bangalore www.scmGalaxy.com, Author - Rajesh Kumar

grep with Regular Expressions grep ‘regular_expression’ file Valid metacharacters . Any single character * Zero or more occurences of the preceding character [aA] Enumeration: a or A [a-f] Any one of the characters in the range of a through f ^a Any lines that start with a z$ Any lines that end with z www.scmGalaxy.com, Author - Rajesh Kumar

grep options -v print lines that do not match -c print only a count of matching lines -l print only the names of the files with matching lines -n number the matching lines -i ignore the case of letters when making comparisons -w do a whole word search www.scmGalaxy.com, Author - Rajesh Kumar

sort command The sort command sorts lines and writes the result to standard output: $ sort [ -t delimiter] [+field[.column]] [options] Options: -d sorts in dictionary order. Only letters, digits and spaces are considered in comarisons -r reverses the order of the specified sort -n sorts numeric fields in arithmetic value www.scmGalaxy.com, Author - Rajesh Kumar

sort examples $ cat animals dog.2 cat.4 elephant.10 rabbit.7 $ sort animals cat.4 dog.2 elephant.10 rabbit.7 $ cat animals | sort +0.1 rabbit.7 cat.4 elephant.10 dog.2 $ cat animals | sort -t. -n +1 dog.2 cat.4 rabbit.7 elephant.10 www.scmGalaxy.com, Author - Rajesh Kumar

find command Search one or more directory structures for files that meet certain specified criteria Display the names of matching files or execute commands against those files find path expression Examples: $ find / -name file1 ---search for files in whole system with name file1 $ find / -user user1 – exec rm { } \; ---search for the files owned by user1 and delete them $ find / -user user1 – ok rm { } \; ---search for the files owned by user1 and delete them interactively www.scmGalaxy.com, Author - Rajesh Kumar

find options -type f ordinary file d directory -size +n larger than "n" blocks -n smaller than "n" blocks n equal to "n" blocks -mtime +x modified more than "x" days ago -x modified less than "x" days ago -perm onum access permissions match "onum" mode access permissin match "mode" -user user1 finds files owned by "user1" -o logical "or" -newer ref searches for files that are newer than the reference file. www.scmGalaxy.com, Author - Rajesh Kumar

cut command Used to cut fields from each line of a file or columns of a table cut –d: -f1,5 /etc/passwd cut –c2 test second character of each line cut –c-2 test first 2 characters of each line www.scmGalaxy.com, Author - Rajesh Kumar

tr command Used to substitute the values tr [a-z] [A-Z] will convert each small letter to caps cat test | tr [a-z] [A-Z] will convert the small letters to caps in display tr –s “ “ will squeeze multiple space occurences of space into one www.scmGalaxy.com, Author - Rajesh Kumar

ftp The ftp Command Syntax : $ ftp hostname get Gets a file from the remote computer. put Sends a local file to the remote system mget get multiple files from the remote system mput Sends multiple files to the remote system cd changes the directory in the remote system lcd changes the directory in the local system ls Lists files on the remote computer. ? Lists all ftp commands help command Display a very brief help message for command. bye Exits ftp. www.scmGalaxy.com, Author - Rajesh Kumar

The paste command Used to paste files vertically eg. file1 file2 paste file1 file2 name address age name address age ram mvm 29 ram mvm 29 raghu rjnagar 25 raghu rjnagar 25 (To rearrange f1 f2 f3 to f3 f2 f1, cut each field,put into file then paste) By default paste uses the tab character for pasting files, but –d to specify one eg. paste –d \| file1 file2 name address|age ram mvm|29 raghu rjnagar|25 www.scmGalaxy.com, Author - Rajesh Kumar

The split command Used to split up the files: This command breaks up the input into several equi line segments. by defalult, split breaks a file into 1000 line pieces(or whatever is left) split creates files like xaa,xab,xac …. xaz then xba, xbb …. xbz and … xzz . So there can be 676(26*26) files split –5 chap (here the chap file is broken into files of 5 lines size) split chap small (the file names will be smallaa,smallab …. smallzz) www.scmGalaxy.com, Author - Rajesh Kumar

The diff(Differential file comparator) Command Analyzes text files Reports the differences between files diff [-options] file1 file2 www.scmGalaxy.com, Author - Rajesh Kumar

The cmp command $ cmp names names.old names names.old differ: byte 6, line 1 $cmp -l names names.old 6 12 151 7 102 156 8 157 145 ... ... ... cmp: EOF on names www.scmGalaxy.com, Author - Rajesh Kumar

The file command The file command tells the type of file Example: $ file /usr/bun/vi /usr/bin/vi:executable (RISC system/6000) or object module $ file c1 c1: ascii text $ file /usr/bin /usr/bin: directory www.scmGalaxy.com, Author - Rajesh Kumar

create a disk archive that contains a group of files or an entire directory structure -c copy -x extract -t list [only one can be present at a time] -f to specify the device name tar [–]cvf etc.tar /etc/* tar (tape archive program) www.scmGalaxy.com, Author - Rajesh Kumar

tar –xvf tarfile Example: tar –xvf etc.tar selective extraction tar –xvf etc.tar /etc/passwd tar –tvf etc.tar will display the archive Restoring Files www.scmGalaxy.com, Author - Rajesh Kumar

Module 10 Controlling Processes www.scmGalaxy.com, Author - Rajesh Kumar

Objectives Upon completing this module you should be able to understand the following: Monitoring Process Controlling Processes Terminating Processes Kill Signals Running Long Processes Job Control www.scmGalaxy.com, Author - Rajesh Kumar

Monitoring Process The ps command dislays process status information $ ps -f UID PID PPID ... TTY ... COMMAND john 202 1 ... tty0 ... -ksh john 204 202 ... tty0 ... ksh john 210 204 ... yyu0 ... ls -R / john 212 204 ... tty0 ... ps -f www.scmGalaxy.com, Author - Rajesh Kumar

Controlling Processes Foreground Processes: $ ls -lR / >lsout Background Processes: $ ls -lR / >lsout & www.scmGalaxy.com, Author - Rajesh Kumar

Terminating Processes Foreground Processes: ctrl-c Interrupt key, cancels a forground process kill Sometimes the kill command is used to terminate foreground processes Background Processes: kill kill is the only way to terminate background processes www.scmGalaxy.com, Author - Rajesh Kumar

Kill Signals Sig Meaning 01 hangup- you logged out while the process was still running 02 interrupt- you pressed the interrupt(break) key sequence ctrl-c 03 quit -you pressed the quit key sequence ctrl-\ 09 Kill signal: The most powerful and risky signal that can be sent Signal cannot be avoided or ignored! 15 Termination signal(Default): Stop a process Signal can be handled by programs www.scmGalaxy.com, Author - Rajesh Kumar

Running Long Processes The nohup command will prevent a process from being killed if you log off the system before it completes: $ nohup ls -lR / >lsout & [1] 100 If you do not redirect output, nohup will redirect output to a file nohup.out $ nohup ls -lR / & [1] 102 Sending output to nohup.out www.scmGalaxy.com, Author - Rajesh Kumar

Job Control jobs Lists all jobs <ctrl-z> Suspends foreground task fg %jobnumber Execute job in foreground bg %jobnumber Execute job in background stop %jobnumber Suspends background task www.scmGalaxy.com, Author - Rajesh Kumar

Job Control Examples $ ls -R / > out 2> errfile & [1] 273 $ jobs [1] + Running ls -R / > out 2>errfile & $ fg %1 ls -R / > out 2>errfile <ctrl-z> [1] + Stopped (SIGTSTP) ls -R / >out 2>errfile & $ bg %1 % jobs [1] + Running ls -R / >out 2>errfile & $ kill %1 [1] + Terminating ls -R / >out 2>errfile & www.scmGalaxy.com, Author - Rajesh Kumar

Module 11 Shell Programming Concepts www.scmGalaxy.com, Author - Rajesh Kumar

Objectives Upon completing this module you should be able to understand the following: echo & read commands Command Line Arguments The logical operators && and || The if Conditional Numeric comparison with test numeric, string and file comparison The case CONDITIONAL expr: Computation Command Substitution sleep & wait while loop, until and for loops www.scmGalaxy.com, Author - Rajesh Kumar

echo & read commands echo used to display messages on the screen read used to accept values from the users, make programming interactive eg. echo “Enter ur name “ read name echo “Good Morning $name” www.scmGalaxy.com, Author - Rajesh Kumar

Command Line Arguments Shell programs can accept values through 1. read [Interactive –used when there are more inputs] 2. From the command Line when u execute it[Non interactive- used when only a few inputs are there] For eg. sh1 20 30 Here 20 & 30 are the command Line arguments. Command Line args are stored in Positional parameters $1 contains the first argument, $2 the second, $3 the third etc. $0 contains the name of the file, $# stores the count of args $* displays all the args www.scmGalaxy.com, Author - Rajesh Kumar

An example of Command Line args. #! /bin/bash echo “Program: $0” echo “The number of args specified is $#” echo “The args are $*” sh sh1 prog1 prog2 www.scmGalaxy.com, Author - Rajesh Kumar

The parameter $? $? can be used to know the exit value of the previous command . This can be used in the shell scripts: www.scmGalaxy.com, Author - Rajesh Kumar

The logical operators && and || These operators can be used to control the execution of command depending on the success/failure of the previous command eg. grep ‘director’ emp1.lst && echo “Pattern found in file” grep ‘manager’ emp2.lst || echo “pattern not found” or grep ‘director’ emp.lst’ && echo “Pattern found” || echo “Pattern not found” www.scmGalaxy.com, Author - Rajesh Kumar

exit : Script Termination exit command used to prematurely terminate a program. It can even take args. eg. grep “$1” $2 | exit 2 echo “Pattern found – Job over” www.scmGalaxy.com, Author - Rajesh Kumar

The if Conditiona l if condition is true then execute commands else execute commands fi else is not a must : if condition is true then execute commands fi www.scmGalaxy.com, Author - Rajesh Kumar

An example of if eg1: if grep “director” emp.lst then echo “Pattern found” else echo “Pattern not found” fi Every if must have an accompanying then and fi , and optionally else www.scmGalaxy.com, Author - Rajesh Kumar

Numeric comparison with test test is used to check a condition and return true or false Relational operators used by if Operator Meaning -eq Equal to -ne Not equal to -gt Greater than -ge Gfreater than or equal to -lt Less than -le Less than or equal to www.scmGalaxy.com, Author - Rajesh Kumar

An example of test with numeric echo “Enter age” read age if test $age –ge 18 then echo “Major” else echo “Minor” fi www.scmGalaxy.com, Author - Rajesh Kumar

[ ] short hand for test echo “Enter age” read age if [ $age –ge 18 ] then echo “Major” else echo “Minor” fi www.scmGalaxy.com, Author - Rajesh Kumar

if –elif :Multi-way Branching if condition echo “Enter marks” then execute commands read marks elif condition if [ $marks –ge 80 ] then execute commands then echo“Distinction” elif condition elif [ $marks –ge 60 ] then execute commands then echo “First Class” else execute conditions else echo “Pass” fi fi can have as many elif , else is optional www.scmGalaxy.com, Author - Rajesh Kumar

test String comparison test with Strings uses = and != String Tests used by test Test Exit Status -n str1 true if str1 is not a null string -z str1 true if str1 is a null string s1 = s2 true if s1 = s2 s1 != s2 true if s1 is not equal to s2 str1 true if str1 is assigned and not null www.scmGalaxy.com, Author - Rajesh Kumar

file tests File related Tests with test Test Exit Status -e file True if file exists -f file True if fie exists and is a regular file -r file True if file exists and is readable -w file True if file exists and is writable -x file True if file exists and is executable -d file True if file exists and is a directory -s file True if the file exists and has a size >0 www.scmGalaxy.com, Author - Rajesh Kumar

The case CONDITIONAL case used to match an expression for more than one alternatives and uses a compact construct to permit multi way branching case expression in pattern1) execute commands;; pattern2) execute commands esac www.scmGalaxy.com, Author - Rajesh Kumar

An example for case echo “1. List of files 2. Processes of user 2. Quit” echo “Enter choice” read choice case “$choice” in 1) ls ;; 2) ps –f ;; 3) exit;; *) echo “Wrong Choice” esac www.scmGalaxy.com, Author - Rajesh Kumar

case Matching Multiple patterns echo “Do u want to continue (y/n) “ read answer case “$answer” in y|Y) echo “Good” ;; n|N) exit ;; esac case can also use wildcards like [yY][eE]* or [nN][oO] www.scmGalaxy.com, Author - Rajesh Kumar

expr: Computation Shell doesn’t have any compute features-depend on expr expr 3 + 5 expr $x + $y expr $x - $y expr $x \* $y expr &x / $y expr $x % $y division gives only integers as expr can handle only integers www.scmGalaxy.com, Author - Rajesh Kumar

Command Substitution x=5 x=`expr $x +1` echo $x it will give 6 www.scmGalaxy.com, Author - Rajesh Kumar

sleep & wait sleep 100 the program sleeps for 100 seconds wait wait for completion of all background processes wait 138 wait for completion of the process 138 www.scmGalaxy.com, Author - Rajesh Kumar

while loop while condition is true do execute commands done eg. x=1 while test $x -le 10 do echo $x x=`expr $x + 1` done ( while true will set infinite condition) www.scmGalaxy.com, Author - Rajesh Kumar

until : while’s complement x=1 until test $x –gt 10 do echo $x x=`expr $x + 1` done www.scmGalaxy.com, Author - Rajesh Kumar

For loop for variable in list do execute commands done eg. for x in 1 2 3 4 5 do echo “Value of x is $x” done www.scmGalaxy.com, Author - Rajesh Kumar

The list in for loop List from variables for var in $PATH $HOME $MAIL do echo $var done 2. List from Wild cards for file in *.c do cc $file –o $file{x} done 3. List from positional parameters for pattern in $* do grep”$pattern” emp.lst || echo “pattern $pattern not found” done 4. List from command substitution for file in `cat clist` www.scmGalaxy.com, Author - Rajesh Kumar

Labs 1.develop a script that accepts a file name as argument and displays the last modification time if the file exists and a suitable message if it doesn’t. 2. write a script that accepts one or more file names as arguments, and converts them all to upper case provided they exist. 3. Devise a script that lists files by modification time when called with lm and by access time when called with la. By default the script should show the listing of all files in the current directory 4. Write a script that uses find to look for a file and echo a suitable message if the file is not found. You must not store the output of the find to a file. 5. use the “if then” construct to write a script that will check for at least two parameters present on the command line. Output an appropriate error message. 6. Write a shell script which will compare two numbers passed as command line arguments and tell which one is bigger. 7. Write a shell script which will add all the numbers between 0 and 9 and display the result. 8. Write a script which will give 4 choices to the user 1. ls 2. pwd 3. who 4. exit and execute the command as per the users choice www.scmGalaxy.com, Author - Rajesh Kumar

Labs contd. 9. Execute the date command with the proper arguments so that its output is in a mm-dd-yy format. 10. From your home directory, make the following directories with a single command line d1, d1/d2, d1/d3, d1/d2/d4 11. create a file f1 in the home directory. Change the permissions to 777. 12. create a file f2 in your home directory and set setuid and sticky bit permissions on the file. 13. Write the command which will display all the files in the system having setuid set. 14. write the command to find all the files in your home directory hierarchy modified 1yr back and having a size more than 10 mb and delete the matching files interactively. 15. write two commands which will display all the ordinary files in the system www.scmGalaxy.com, Author - Rajesh Kumar

Labs contd. 16. Write a script that lists all the start scripts in a specified rc#.d directory a. Name the script rcscripts b. Write the script so that it doesn’t require command-line arguments c. For all start scripts in /etc/rc3.d directory print The script name The inode number of the script All other files under /etc with the same inode number 17.Print all entries from /etc/passwd for users who have ksh as their login shell 18. Print the lines from /etc/group that contain the pattern root preceded by the line number 19. Print the number of users in the system. 20. Print the users whose account is locked www.scmGalaxy.com, Author - Rajesh Kumar

Basic Unix

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