Unix in a Nutshell, 4th Edition

Simple Pattern-Action Examples

• Print first field of each line:

      { print $1 }

• Print all lines that contain pattern:

      /pattern/

• Print first field of lines that contain pattern:

      /pattern/ { print $1 }

• Select records containing more than two fields:

      NF > 2

• Interpret input records as a group of lines up to a blank line. Each line is a single field:

      BEGIN { FS = "\n"; RS = "" }

• Print fields 2 and 3 in switched order, but only on lines whose first field matches the string URGENT:

      $1 ~ /URGENT/ { print $3, $2 }

• Count and print the number of lines matching pattern:

      /pattern/ { ++x }
      END { print x }

• Add numbers in second column and print the total:

      { total += $2 }
      END { print "column total is", total}

• Print lines that contain fewer than 20 characters:

      length($0) < 20

• Print each line that begins with Name: and that contains exactly 7 fields:

      NF == 7 && /^Name:/

• Print the fields of each record in reverse order, one per line:

      {
              for (i = NF; i >= 1; i--)
                      print $i
      }