HSBC Global Technology

1. HSBC Global Technology UNIX -Kirtikumar Shinde

2. Topics 1. Introduction • Unix Filesystem • File Permissions • Advanced Commands • Shell • Shell Programming • AWK • My Learnings • Questions?

3. Introduction • Multi-user and Multitasking OS • Mostly Written in C at Bell Labs • Most of the servers are on Unix • Unix Flavors • Solaris • HP • AIX • Linux • Current DS Server – Which Unix?

4. Introduction • Architecture

5. / etc bin export dev tmp . . . . . . . . . date user . . . cal home ad . . . . . . . s3910120 exam.txt proj1 work hobby.c . . . . . . Unix File System • An upside-down Tree

6. group others owner 1 1 1 1 1 0 1 0 0 r x r - - r - w x execution writing reading File permissions • Changing permissions • chmod g+w empl.txt • chmod 754 empl.txt • Changing ownership • chown gcdv_dev empl.txt • Changing group • chgrp develp empl.txt

7. Advanced Commands • Sort • Sorts the contents of a file. • sort [-b f n r o t] [file name(s)] • Takes the contents of a file(s) and displays it in sorted order. • Flags: -b ignores blanks -f change all lower case letter to upper case before comparing -n numeric sort -r reverse usual order -o sends output of command to some file -t field delimiter • E.g. To sort the Emp.txt on 2nd field in reverse order $sort -t, -n -r +2 Emp.txt

8. Advanced Commands • grep • Searches a file for pattern. • grep [-c i l v] <pattern> [file name(s)] • Takes the contents of a file(s) and displays it in sorted order. • Flags: -c displays count of matching lines. -i ignore the case while searching -l lists the names of files that matches pattern -v displays all lines that don’t contain the pattern • E.g.To display all lines in the ‘Emp.txt’ that match either the abc or xyz string: $grep "abc|xyz" Emp.txt

9. Advanced Commands • tar • Compression and decompression of files. • tar -(x|c) [ v f r] <tarfile> [file name(s)] • Flags: -x extract from file. -c create new extract file. -v displays list files -f name of file follows -r append to old extract. • E.g. • To compress file Emp.txt$tar -cvf Emp.tar Emp.txt • To decompress file Emp.tar$tar -xvf Emp.tar

10. Shell • Command interpreter that waits for commands, executes them and displays the results • Bourne shell • Developed by Steve Bourne at AT&T • Korn shell • Developed by David Korn at AT&T • C-shell • Developed by Bill Joy for Berkeley Unix

11. Shell • Shell works as follows: • Shell displays a prompt. • You type in a command. • You press the return key. • The shell interprets the commands typed and tries to find the correct programs to run. • The kernel runs the requested programs and returns the results to the shell. • The shell displays the command prompt again

12. Shell • Which Shell I am in ? • finger –m myusername • Know your shell – Korn Shell – its features • Aliases – It allows shorthand for commands. • Command history – Lets you recall previously entered commands. • Command line editing – Allows us to edit commands vi style. • Integrated programming features – It enables common programming tasks to be done cleanly & without creating extra processes. • Support regular expressions. • Advanced I/O features – Ability to carry out two way communication with concurrent processes. • Increased speed of shell code execution. • Has highly robust security features.

13. Shell • Shell system variables • PATH = Defines path shell must search in order to execute any command or file. • HOME = Indicates default working directory of the user. • PS1 = System prompt 1. • PS2 = System prompt 2, default value is “>”.

14. UNIX Shell Programming • Shell Script (Shell Procedure) • A program written in shell programming language is known as a shell script or shell procedure. • Shell Programming Language • The shell programming language is a command language with a lot of features common to many computer programming languages, including the structured language constructs: sequence, selection, and iteration. • Command Languages • Command languages are interpreted languages • It allows then use of Unix commands in scripts

15. UNIX Shell Programming • Shell scripting keywords. • Please Note : Script variables shouldn’t be same as keywords. • Looping constructs, to be discussed in coming slides. • set, unset • Readonly • Exit • Ulimit • Umask

16. UNIX Shell Programming • Create - Simple Hello World shell script. #!/bin/sh echo "Hello World“ • Make Files Executable • $ chmod 777HelloWorld.sh • Execute the shell script • Observe the output ‘Hello World’ will be between two command prompts. $ HelloWorld.sh

17. UNIX Shell Programming • Assignments • Value assignments. • String assignment – var=“Your Name” • Think if not within double quotes. $echo $var • think if not $ • Making variable readonly.a=50readonly a

18. UNIX Shell Programming • echo and Escape Characters • Display strings as “printf” in C • The echo command recognizes escape characters. Escape characters all start with the backslash ( \ ), and you can use them as part of the echo command argument string. • E.g. • $ echo “\nHello\n”

19. UNIX Shell Programming • Passing parameters to a Shell script • Consider Welcome.sh, & we are sending name as parameter to a Shell Script.Welcome.sh Vikram • think If you want to send First name & Last name as one parameter. In above case 0th parameter value considered will be script name.1st parameter value considered will be name, i.e.Vikram. • Accessing parameters in a Shell script • Parameter to a shell script starts from index 1. Its value is retrieved by using $1 & so on. … Think how you will access parameter beyond 9th parameter.

20. UNIX Shell Programming • Shell Positional Variable $0 : command itself $1 : first parameter $n : nth parameter $# : no. of parameters $? : exit status of last command executed $* : all parameters $$ : process number of shell $! : PID of last background process

21. UNIX Shell Programming • if-then and if-then-else • The if-then Construct if [ condition ] then true-commands fi • The if-then-else Construct if [ condition ] then true-commands else false-command(s) fi

22. UNIX Shell Programming • if-then-elif if [ condition1 ] then commands_1 elif [ condition2 ] then commands_2 else commands_n fi

23. UNIX Shell Programming • test Command • The test command is a built-in shell command that evaluates the expression given to it as an argument and return true if the expression is true, if otherwise, false. • You can use square brackets ( [ ] ) instead of the word test. • Example • if test $str1 = $str2 then echo “Something”fi • if [$str1 = $str2] then echo “Something”fi

24. UNIX Shell Programming • Logical Operators -a AND Operator -o OR Operator ! NOT Operator • Numeric Test Operators -eq Is number1 equal to number2 ? -ne Is number1 not equal to number2 ? -gt Is number1 great than number2 ? -ge Is number1 great than or equal to number2 ? -ltIs number1 less than number2 ? -le Is number1 less than or equal to number2 ? • E.g if test $var –lt 10then echo “Something”fi

25. UNIX Shell Programming • String Test Operators string1 = string2Does string1 match string2? string1 != string2Does string1 not match string2? -n stringDoes string contain characters? -z string Is string an empty string? • E.g. if test $str1 = $str2 then echo “Something”fi • Think if no space on both sides of an operator

26. UNIX Shell Programming • File Test Operators -s file True if File size is greater than 0 -f file True if File exists & not a directory -d file True if file exists & is a directory file. -r file True if file exists & you have read permission on it. -w file True if file exists & you have write permission on it. -x file True if file exists & you have execute permission on it. • E.g if [ –f $filename ]then echo “Something”fi • Think if no space on both sides of an option.

27. UNIX Shell Programming • The expr Command • Arithmetic Operators +: Addition operator -: Subtraction operator /: Division operator *: Multiplication operator %: Remainder operator • Expressions • Arithmetic expressiona=`expr $a + $b` … think if no space both the sides of + & space both the sides of =. • Floating point arithmetic expressiona=`expr $a + $b | bc` • String expressionpath=$path1”/”$path2

28. UNIX Shell Programming • While Loop while [ condition ] do command(s) done • For Loop for variable in list-of-value do command(s) done

29. AWK • Introduction to awk. • awk is a programming language designed to search for, match patterns, and perform actions on files. awk programs are generally quite small, and are interpreted. • awk scans input lines one after the other, searching each line to see if it matches a set of patterns or conditions specified in the awk program. For each pattern, an action is specified. The action is performed when the pattern matches that of the input line. • Sample awk command:awk ‘/pattern/’’{print $0}’ file1

30. My Learnings • When I will go for Shell scripting. • Automating my regular tasks. • Customizing my work environment. • Task is pretty simple • When I will avoid Shell scripting. • It needs interaction with multiple applications. • Problem is relatively complex involves more than one tool. • Lookups or finding data.

31. Questions ?

32. Thank You