AWK 101

Note for Learning Awk Is Essential For Linux Users

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awk is a tool to process text, line by line.

Variable

$0 means whole line, $1 means the first column, NF means the last column, ‘NR’ means nubmer of row. etc.

• List process name

  ps | awk '{print $1}' 
  

Seperator

use : as seperator (default is space), print out the first, 6th and 7th column. use Tab between them.

awk -F ":" '{print $1"\t"$6"\t"$7}' /etc/passwd

Change Seperator as output

use : as seperator, output use Tab as seperator, print out the first, 6th and 7th column. (Use comma in between, so they are columns, and awk can insert Tab in between.

awk 'BEGIN{FS=":"; OFS="\t"} {print $1, $6, $7}' /etc/passwd

Print last column

search the line start with ‘/’, use ‘/’ as seperator, print out the last column.

awk -F "/" '/^\// {print $NF}' /etc/shells

function

• print lines which is longer than 7

  awk 'length($0) > 7' /etc/shells
  

• print all bash process

  awk 'length($0) > 7' /etc/shells
  

• substring