AWK : Commands

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 AWK

AWK stands for "Aho, Weinberger, and Kernighan". It is named after its creators Alfred Aho, Peter Weinberger, and Brian Kernighan, who developed the language while working at Bell Labs in the 1970s.


replace a word with another word

awk '{gsub(/sreejith/, "Balakrishnan"); print}' filename  // This will replace all the sreejith to Balakrishnan

Print a particular word if that appears in the file

awk '{for(i=1;i<=NF;i++) if ($i == "word") print $0}' filename

Print only once if a word was found in the file

awk '{for (i=1; i<=NF; i++) if ($i == "sreejith" && !seen[$i]++) print $i}' test-file.txt 

 Print the last word that has "america" as its last word

awk '$NF ~ /america$/' test-file.txt
or
awk '$NF ~ /america$/{print $0}' test-file.txt

1. awk '{print}' filename: This command simply prints the entire contents of the specified file.
   
   awk '{print $1 " :  "$2}' filename

2. awk '/pattern/' filename: This command prints all lines in the file that match the specified pattern.

3. awk '/pattern/ {print $1}' filename: This command prints the first field (i.e., the first column) of all lines in the file that match the specified pattern.

4. awk '{print $1,$3}' filename: This command prints the first and third fields (i.e., columns) of all lines in the file.

5. awk '{sum += $1} END {print sum}' filename: This command calculates the sum of the first field in the file and prints the result at the end of processing.
   

6. awk -f "," 'NR! =1{print $1} filename -- This will skip the first row NR - stands for no of rows. skipping the header

7. awk 'NR!=1{print $1 " : " $2 " : " $3}' FS=" " test-file.txt

8. awk 'NR==3 {print}' filename: This command prints the third line of the file.

9. awk '{print NR,$0}' filename: This command prints the line number and the entire line for each line in the file.

10. awk -F':' '{print $1}' /etc/passwd: This command prints the first field (i.e., username) of each line in the "/etc/passwd" file, where fields are separated by colons.
    awl '{print $1} FS="|" filename

11. awk '/pattern/{print $0 > "outputfile"}' filename: This command writes all lines in the file that match the specified pattern to an output file named "outputfile".

12. awk '{gsub(/oldpattern/, "newpattern")} {print}' filename: This command replaces all occurrences of "oldpattern" with "newpattern" in each line of the file and then prints the modified line.

 

Sure! Here are some more AWK commands:

1. awk 'BEGIN{print "Start processing file"}{print $0}END{print "End of file"}' filename: This command prints a message at the beginning and end of processing a file, and prints each line in between.

2. awk '/pattern/{print "Match found: " $0}' filename: This command prints a message before each line that matches the specified pattern.

3. awk '$1 > 50{print $2}' filename: This command prints the second field (i.e., column) of all lines in the file where the first field is greater than 50.

4. awk '{if($1 == "pattern"){print}}' filename: This command prints all lines in the file where the first field is equal to "pattern".

5. awk '{print NF,$0}' filename: This command prints the number of fields (i.e., columns) and the entire line for each line in the file.

6. awk '{for(i=1;i<=NF;i++){if($i ~ /pattern/){print $i}}}' filename: This command prints all fields that contain the specified pattern for each line in the file.

7. awk '{print length($0)}' filename: This command prints the length of each line in the file.

8. awk 'NR==FNR{a[$1]=$2;next}{if($1 in a){print a[$1],$2}}' file1 file2: This command reads file1 and creates an associative array "a" with the first field as key and second field as value. It then reads file2 and prints the value corresponding to the first field in file1 and the second field in file2 if the first field is present in file1.

9. awk 'length($0) > 10{print substr($0,1,10) "..."}' filename: This command prints the first 10 characters of each line in the file, followed by ellipsis ("..."), for lines longer than 10 characters.

10. awk '{sum += $1} NR%5 == 0{print "Sum of every 5 lines: " sum; sum=0} END{print "Final sum: " sum}' filename: This command calculates the sum of the first field for every 5 lines in the file, and prints the partial sums and the final sum at the end of processing.
    
    
    
    

====UDMY

We are going to fetch data from a file where each column is seaperated by space

Fetching any specific column from a file.

awk '{print $1}' <file_name>   

In this case we are not giving any seperator - by default space is the seperator.

Fetching multiple column at a time.

awk '{print $1 " , " $2}' filename

Fetching data in any specific order

change the order 

awk '{print $3 " , " $2 " , " $1 }' filename

Fetch complete data from a file (All rows and all column)

awk '{print $0}' 

How can we fetch data by giving some separator value.

awk -F  " , "  '{print $1}' filename

--> awk -F " , "  -- if the file is separated by comma

-- > awk -F " | " -- if the file is separated by pipe symbol 

you can even use FS=" | "  instead of awk -F  -- this will also work

awk  '{print $1}' FS=","  filename 

 

FS=" "  -- is given after the print command and awk -F is given before the print

How to display row , or choose rows of your choice where you can modify in such a way that your

chosen row and column is chosen

I do not want to display the header but I want to display all the record alone.

awk -F " , "  'NR!=1{print $1 "   " $2" filename

-- here NR -- No of rows not equal to 1 

If you want to print only the header 

awk -F ", " 'NR==1{print $1 "    " $2}' filename

if you want to display only row number 5

awk -f  " , " 'NR==5{print $1  "      "  $2}' filename

If you want to display all rows which are below the row number 7 or equal to 7

awk -f  " , " 'NR<=7{print $1  "      "  $2}' filename

And command NR>1 && NR

awk -F " ," 'NR>1 && NR<=7{print $1 "   " $3 "      "  $4}' filename

OR command NR>1 ||  NR

awk -F " ," 'NR<5  ||  NR>=407{print $1 "   " $3 "      "  $4}' filename

Directing the output to a file

awk -F " ," 'NR<5  ||  NR>=407{print $1 "   " $3 "      "  $4}' filename >  awk_result.txt

Conditional select data 

awk -F " , "  '$1==9{print $1 "  , " $2}' filename

awk -F " , "  '$1>30{print $1 "  , " $2}' filename

Display only , this will display column 1 where the name is Roger Nick

awk -F " , " "$1=="Roger Nick"{print $1 "   " $2  "    "  $3} filename

The below will display the complete line where the condition of the name is met.

awk -F " , " "$1=="Roger Nick"{print $0} filename

Using substring to print all the row wherever you find the substring

Display all the rows that do not have gmail.com in them

awk -R "," '!/gmail.com/{print $0}  filename

I believe it it tild symbol but he say acute symbol

awk -R "," '$1~"U"{print $0}  filename

The above will display all the lines that has U

Not equal -- to search substring

awk -R "," '$1!~"U"{print $0}  filename

====

AWK -- Find text at the start of a line

awk -F  ","  '$1~/a/{print $0} filename

what if you want to print out all the rows that begin with "a"

awk -F  ","  '$1~/^a/{print $0} filename

display all rows where "n" is the last character 

AWK with If statement

awk -F " | " '{if ($3=> 25000) print $0;}' filename

AWK IF condition with && 

IF & ELSE WITH AWK 

awk -F " | "  '{ if  ($3>20000) print $2;

else print "*****" ; }' filename

IF ELSE / IF ELSE

BLOCKS AND LOOPS : AWK 

Here we need a header to be displayed and therefore we are using BEGIN BLOCK

Multiplying salary twice 

AWK END Block

AWK : While :

FOR LOOP AWK 

All the lines in the file is displayed twice. 

Storing a AWK result to a variable

Splitting the file into different files bases on the column number 3

awk -F " " '{print > $3}' test-file.txt 

Splitting the files into multiple files by column data

awk -F " " '{print $1 " "$2 " " $3 > $6 }' filename  -- on the basis of column 6 the file will be split.

length of the string values.

awk -F " "  '{print $12 "       "  length($2}' filename

$ awk -F " " '{print $2 "            " length($2)}' test-file.txt 

Phone            5

7989849494            10

7989849494            10

7989849494            10

Functions : touppper / to lower

$ awk -F " " '{print $2 "            " length($2)}' test-file.txt 

Phone            5

7989849494            10

7989849494            10

7989849494            10

string functions

$ awk -F " " '{sub(/sreejith/,"SEETA", $1);print $1}' test-file.txt

Name

RAVANAN

RAVANAN

RAVANAN

RAVANAN

Name

SEETA

SEETA

SEETA

SEETA

SEETA

SEETA

SEETA

$ awk -F " " '{sub("sreejith","RAVANAN", $1);print $1}' test-file.txt

Name

RAVANAN

RAVANAN

RAVANAN

awk '{gsub(/sreejith/, "Balakrishnan"); print}' filename  // This will replace all the sreejith to Balakrishnan

gsub -- subsitutes globally

$ awk -F " " '{gsub("sreejith","RAVANAN", $1);print $1}' test-file.txt

Find Index number

awk -F " " '{print index($3 , "L")}' filename  //here it find the index of 3rd column wherever there is "L" character. index postion on the word is displayed.

$ awk -F " " '{print index($3 , "L")}' test-file.txt 

0

1

1

1

1

Substr:

$ awk -F "," '{print substr($2, 1, 4)}' filename

$ awk -F " " '{print substr($3, 1, 4)}' test-file.txt

addr

Lond

Lond

AWK Printf 

printf is used for formatting the results

%s - string

%d - integer data

change the alignment to left 

Zero before the value