awk

awk script outline

• #!/usr/bin/awk -f
• BEGIN {action}
• pattern {action}
  if no pattern, do action for every line
  if no action, print matching lines
• END {action}

Misc

• fields for each record (line) are broken into variables $1, $2...

Variables

• NF (number of fields) in current record, $NF is value of last field
• NR (number of record) is current record#
• FS (field separator) usually blank, can also set with -F on command line
• RS (record separator) usually a newline; do RS="" when records are multiple lines with each record separated by a blank line
• OFS (output field separator) is usually blank
• ORS (output record separator) is usually newline

examples

• echo "Hello, world." > hello.txt
  awk '{print}' < hello.txt
• awk 'BEGIN {print Hello}'

Links

• sed & awk
• gawk
• tutorial from Greg Goebel
• dmoz