How to use the awk command

Hello everyone.
I'm Okazaki from the System Solutions Department.
This time, I'll be writing about the awk command, which is also used when checking logs.

What is the awk command?

This command allows you to output only data from specific columns or calculate total values ​​when processing multiple lines of data separated by spaces or specific characters

awk '{print$[number of columns you want to output];}'

For example, there is a file like this:

test.txt 1 2 3 5 1 2 3 6 1 2 3 7 1 2 3 8

If you want to display only the first column, you can do so as follows:

cat test.txt | awk '{print$1;}' 1 1 1 1

How to use

To use any character as a delimiter:

awk -F [delimiter] '{print$1;}'

• Usage example

Show only the second column

sed -e 's/ /:/g' test.txt | awk -F ':' '{print$2;}' 2 2 2 2

To output line numbers:

awk '{print NR $1;}'

• Usage example

Show only the third column

sed -e 's/ /:/g' test.txt | awk -F ':' '{print NR $3;}' 13 23 33 43

However, this is difficult to understand, so do it like this:

sed -e 's/ /:/g' test.txt | awk -F ':' '{print NR " " $3;}' 1 3 2 3 3 3 4 3

To output rows where a specific column contains a specific string:

awk '$1==[any character]'

• Usage example

Only 5 is displayed on the fourth line

sed -e 's/ /:/g' test.txt | awk -F ':' '$4=="5" {print NR " " $4;}' 1 5

In the opposite case

sed -e 's/ /:/g' test.txt | awk -F ':' '$4!="5" {print NR " " $4;}' 2 6 3 7 4 8

To sum the numbers in a specific column:

awk '{sum+=$1;}END{print sum;}'

• Usage example

Display the total on the first line

sed -e 's/ /:/g' test.txt | awk -F ':' '{sum+=$1;}END{print sum;}' 4

In the case of the average value

sed -e 's/ /:/g' test.txt | awk -F ':' '{sum+=$1;}END{print sum/NR;}' 1

summary

You will likely need to open log files frequently during operations, but
formatting the file before opening it will make it easier to read and
will allow you to more efficiently aggregate errors and accesses.
Using this awk command in conjunction with other commands in your daily operations will help improve the efficiency of your operations.

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