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4.Brief commands overview

The language looks a little like C but automatically handles input, field splitting, initialization, and memory management.

  • Built-in string and number data types
  • No variable type declarations
data[1]= 330                   
data[3]= "text"     # yes, the elements could be of different type
data[7]= 7.5                   
data["Monday"]= 1               

awk is a great prototyping language

  • start with a few lines and keep adding until it does what you want

awk gets its input from

  • files
  • redirection and pipes
  • directly from standard input

Common commands and constructions - examples


for (i=1; i<=10; i++) {
  print i

If else statement

if ($1 > 2) {
  print $2 
} else if ($1 < 2) {
  print $3 
} else {
  print $3 
  • time to add a bit more, so we can get some meaningful calculations on our data Exercises/Warming up.

While statement

while ($1 < $3) {
  getline; print


print "Text"$1"more text"

printf ("Text %g more text", $1)

next    #  (skips the remaining patterns on the current line of input)

exit    #  (skips the rest of the current line)

Predefined variables

  • NR - Number of records processed
  • FNR - Number of record processed in the current file while NR refers to the total record number. For the first file FNR==NR, but for the second FNR will restart from 1 while NR will continue to increment.
  • NF - Number of fields in current record
  • FILENAME - name of current input file
  • FS - Field separator, space or TAB by default
  • OFS - Output field separator, space by default
  • ARGC/ARGV - Argument Count, Argument Value array - get arguments from the command line

$1 - first field value, $2 - second etc.

$0 - contains the entire line

Built-in functions


sin(), cos(), atan(), exp(), int(), log(), rand(), sqrt()

String manipulation functions

length(), substitution, find substrings, split strings


print, printf(), print and printf to file


system() - executes a Unix command e.g., system("date") to execute "date" command. Note double quotes around the Unix command

If you have reached this point, perhaps you are already asking where you can read something to begin with. This site is perhaps good for beginners: