Where are the simple AWK examples to get started?

All of my codes fail. They should print "he", "hello" and "5 \n 3", respectively:

awk -v e='he' {print $e}       // not working, why?
awk NF { print hello }
awk { print ARGV[5,3] }

Are there some simple examples about AWK?

From stackoverflow

• For the first, you don't use $ for variables inside awk, try this instead:

  fury> echo | awk -v e='he' '{print e}'
  he
  

  For the second, your condition NF means NF!=0 so it will only print for non empty lines:

  fury> echo | awk 'NF {print "hello"}'
  fury> echo "7 8" | awk 'NF {print "hello"}'
  hello
  

  I've never seen your syntax for the third one, ARGV is a single dimensional array, so you can use:

  fury> awk 'BEGIN {print ARGV[5]}' 1 2 3 4 5 6 7
  5
  fury> awk 'BEGIN {print ARGV[5] "\n" ARGV[3]}' 1 2 3 4 5 6 7
  5
  3
  

  Note I'm using a BEGIN block for the third, otherwise it'll try to open and process 1, 2, 3, ... as files.

  Masi : What about with different arrays? Can I divide the elements of different arrays by one another, like: 1 DIVIDE 2 2 DIVIDE 4 => 0,5 0,5 Possible?

• I use this site. The O'Reilly Sed & Awk book is good as well.

• Try:

  echo "hello" | awk ' {print $0} '
  echo "hello" | awk ' {print $1} '
  

  Note that $0 returns the whole record, and $1 just the first entry; awk starts its counters at 1. So

  echo "hello1 hello2 hello3" | awk ' {print $0} '
  

  returns hello1 hello2 hello3. While

  echo "hello1 hello2 hello3" | awk ' {print $3} '
  

  will return hello3

  I like this awk tutorial.

• First, basic shell scripting sanity:

  • Always enclose your script in single quotes

  Note that the script is a single argument - or a filename with '-f file'.

  An awk script is a sequence of '<pattern> <action>' pairs. The action is enclosed in braces '{}' for clarity - and sanity, again.

  As Pax said, the first example should be:

  awk -v -e e='he' '{ print e }'
  

  The second example is inscrutable - you probably meant:

  awk '{ print "hello" }'
  

  The variable NF is the number of fields on the line. You might get awk to interpret

  awk 'NF { print "hello" }'
  

  as if there is any data on the input line (NF != 0, or number of fields is not zero), then print 'hello'.

  The last example is likewise inscrutable; ARGV is an array of the arguments to 'awk', and the command line provided none. But it is a one-dimensional array. Your sub-scripting notation wants to treat it like a Python dictionary or Perl hash, with two indexes combined. You're OK - awk supports associative arrays; but since you didn't add anything to the array at ARGV[5,2], it won't print anything.

• nice tutorial on http://www.w3reference.com

  Dennis Williamson : Direct link: http://awk.w3reference.com

• Also, lots of useful info and tutorials at http://awk.info