Use of AWK / SED Prof. Navrati Saxena TA: Rochak Sachan

Transcription

1 Use of AWK / SED Prof. Navrati Saxena TA: Rochak Sachan 1

2 CONTENTS 1. AWK 1.1 WHAT IS AWK? 1.2 GENERAL SYNTAX OF AWK 1.3 DOING ARITHMETIC WITH AWK 1.4 VAR. IN AWK 1.4 AWK MISCELLANEOUS 2. SED 2.1 WHAT IS SED? 2.2 OPTIONS OF SED 2.3 EXAMPLES 2

3 WHAT IS AWK? Powerful data manipulation/scripting programming language. Designed by A.V.Aho, P.J.Weinberger, B.Kernigham "AWK is a language for processing files of text. A file is treated as a sequence of records, and by default each line is a record. A.V.Aho 3

4 GENERAL SYNTAX OF AWK awk pattern filename awk { action } filename Ex. awk {print $1} students awk pattern { action } filename students John physics 60 Rick Mechanical 70 Jack Computer 80 Larry Chemical 90 Paul Electrical 88 Ex) awk $3 > 80 {print $1} students awk pattern {action} pattern {action} filename 4

5 GENERAL SYNTAX OF AWK awk f pattern-action-file filename Pattern Execute before reading action /re/ read which match with re Ex) $cat > print_pen /pen/ {print $3} $awk f print_pen list list 1 pen pencil cola rubber notebook

6 PREDEFINED VAR. OF AWK $cat > awk_2 { print # NR is $1 $2 $3. field for this record is NF } $awk f awk_2 list 6

7 GENERAL SYNTAX OF AWK Action Sets of Statements. Statements are separated by ; print, printf, if, while, for, do, break, etc. Ex) $cat awk_1 { if ($2 ~ /^p/) printf %s\n, $0 > pfile if ($2 ~ /^c/) printf %s\n, $0 > cfile } $awk f awk_1 list 7

8 DOING ARITHMETIC WITH AWK operator Commands Meaning =, +=, -=, *=, /=, %= Assignment +, -, /, *, %, ++, -- Arithmetic, &&,! Logic <, <=, ==,!= Comparison v ~p, v!~p pattern $cat > awk_3 {print $1 $2 total price $3 * $4} $awk f awk_3 list 8

9 DOING ARITHMETIC WITH AWK $cat > math { print $1 + $2 = $1 + $2 print $1 - $2 = $1 - $2 print $1 * $2 = $1 * $2 } $awk f math

10 USER DEFINED VARIABLES IN AWK $cat > bill { total = $3 * $4 recno = $1 item = $2 print recno item = total } $ awk f bill list 10

11 USER DEFINED VARIABLES IN AWK How can we get grand total? Grand total printed at the end of all record BEGIN and END patterns of awk 11

12 USER DEFINED VARIABLES IN AWK BEGIN instruct awk, that perform BEGIN action before the first line has been read from database file. END instruct awk, that perform END actions after reading all lines from the database file. BEGIN { action 1 action 2 } { action } END { action 1 action 2. } 12

13 USE OF PRINTF STATEMENT printf format,var1, var2, varn (cf. print var1 var2) 13

14 USE OF PRINTF STATEMENT Commands Meaning \n is used to print new line \t For tab \a Alert or bell \ Print double quote etc %c Character %d Decimal %s String %x Hexadecimal 14

15 USE OF Format Specification Code %10s : left array %6.2f : 소수점아래 2 까지 %-10s : right array 15

16 IF CONDITION IN AWK if ( condition) { statement1 statement2 statementn if condition is TRUE } else { statement1 statement2 statementn if condition is FALSE } 16

17 Loops in awk for (expr1; condition; expr2) { statement1 statement2 statementn } 17

18 Loops in awk while (condition) { statement1 statement2 statementn Continue as long as given condition is TRUE} 18

19 awk miscellaneous(1) awk script to take input from keyboard while running program Example) Run as $awk f testusrip Your name please : Rochak Rochak your age please : 26 Hello Rochak, next year you will be 27 19

20 awk miscellaneous(2) Getline function is used to read input from keyboard & assign the data to variable Syntax) getline variable-name < : getline is function name 2 : variable-name is used to assign the value read from input 3 : Means read from standard input (keyboard) 20

21 awk miscellaneous(3) Reading input From pipe use following Example) Run as $awk f awkread_file Mon Dec 4 02:20:30 IST

22 SED(1) SED is a stream editor. SED is used to perform basic text transformations on an input stream; and SED works by making only one pass over the input & consequently more efficient. But it is SED s ability to filter text in a pipeline which particularly distinguishes it from other types of editors Commands Sed Meaning Start the sed command s/linux/unix(system v)/ Use substitute command to replace Linux with Unix(system v) demofile1 Read the data from demofile1 22

23 SED(2) Option Meaning Example -e -f -n Read the different sed command from command line Read the sed command from sed script file Suppress the output of sed command $sed e s/linux/unix(system v)/ demofile1 $sed f chgrb.sed friends.tdb $sed n /^*.. $/p demofile2 Syntax) Sed option general expression [data-file] Sed option sed-script-file [data-file] 23

24 SED(3) How to write sed script Sed command can be grouped together in one text file -> sed script Example) Run as $sed f chg1.sed inven1 Price of all items changes from 1 st -April Pen Pencil Rubber Cock Inven1 1. Pen Pencil Rubber Cock

25 SED(4) More commands & examples of sed Commands Explnation ^ Beginning of line * Find the asterisk or star.. Followed by any two character $ End of line /p Print the pattern 25

26 SED(5) Matching any number of occurrence Example) Run as $sed f dem_gsed demofile2 > /tmp/fi.$$ $cat /tmp/fi.$$ It can be found all line between *** and *** & delete blank line Demofile2 ************************ abcdefg *** Okay Linux is just like a star. Star brings good things to life When I was little kid I love to see star, my mother says star are Gods Gift to Us! Is their any relation between star and Linux *** 26

27 SED(6) More expression of sed Expression Meaning ^ Beginning of line * Find the asterisk or star {2,3 } Find next two asterisk $ End of line, Next range or search pattern ^ * {2,3 }$ d Now delete all lines between *** and *** range

28 SED(6) Need demofile3 for this purpose Example) Demofile3 Welcome to world of sed what sed is? I don't know what sed is but I think Run as $sed f rmblksp demofile3 Welcome to world of sed what sed is? I don t know what sed is but I think Rani knows what sed Is It can removes all blank line and converts mutiple spaces into single space 28

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30 THANK YOU 30