Awk

awk reads input line by line (a record) and splits each line into fields at whitespace, or at the separator given with -F. A program is a list of pattern { action } pairs; the action runs for every line that matches the pattern.

flowchart LR
  line["root:x:0:0:root:/root:/bin/bash<br/>split with -F ':'"] --> f1["$1<br/>root"]
  line --> f3["$3<br/>0"]
  line --> f7["$7 = $NF<br/>/bin/bash"]

Command	Effect
`awk '{print $5}' file`	Prints the fifth field of every line.
`awk '/foo/ {print $2}' file`	Prints the second field of lines containing `foo`.
`awk -F ',' '{print $NF}' file`	Prints the last field of comma-separated lines.
`awk -F: '$3 >= 1000 {print $1}' /etc/passwd`	Lists regular users (UID 1000 and above).
`awk 'NR > 1' file`	Skips the header line (`NR` is the line number).
`awk 'NF' file`	Drops empty lines (`NF` is the number of fields).
`awk '{sum += $1} END {print sum}' file`	Sums the first column. `END` runs after the last line.
`awk '{print $1, $3}' OFS='\t' file`	Prints two fields separated by a tab.
`awk '!seen[$0]++' file`	Removes duplicate lines while keeping the order.