awk Programming 

• int(x)
  Returns the (nearest) integer value between x and 0.
  Example:

  awk 'BEGIN {sum=22.55; print int(sum) }'
  22

• sqrt(x)
  Square root
  Example:

  awk 'BEGIN {sum=25; print sqrt(sum) }'
  5

• exp(x)
  Exponential of ex
  Example:

  awk 'BEGIN {sum=3; print exp(sum) }'
  20.0855

  Note: e is the base of natural logarithms: 2.7182818284...


• log(x)
  Natural logarithm of x if x is positive. (The power / exponent of e to equal x.) Otherwise returns error.
  Example:

  awk 'BEGIN {sum=10; print log(10) }'
  2.30259

• sin(x)
  Sine of x, with x in radians.
  Example:

  awk 'BEGIN {sum=30; print sin(sum) }'
  -0.988032

• cos(x)
  Cosine of x, with x in radians
  Example:

  awk 'BEGIN {sum=30; print cos(sum) }'
  0.154251

• atan2(y,x)
  Arctangent of y/x in radians
  Example:

  awk 'BEGIN { angle=atan2(1,2);print angle }'
  0.463648

• rand()
  Random number between 0 and 1. Never 0 or 1.
  Example:

  awk 'BEGIN { guess=rand();print guess }'
  0.840188

  Note: rand generates from the same seed, thus repeated execution of a script produces the same result. Use srand to change the seed.


• srand(x)
  Set the seed for generating random numbers to x.
  Example:

  awk 'BEGIN {srand(100); {print rand() i++}}'
  0.3155980

  If the x argument is left out, the seed is the current date and time of day. Use this for more 'random' numbers.

CAUTION: A number of functions deal with indices into strings. For these functions, the first character of a string is at position (index) one. This is different from C and the languages descended from it, where the first character is at position zero. You need to remember this when doing index calculations, particularly if you are used to C.

• index(in,find)
  Look in the string 'in' for the string 'find'. Returns the character position (index) of the first occurrence of 'find'.
  Example:

  awk 'BEGIN {print index("discombobulation","u")}'
  10

• length(string)
  Return the number of characters in 'string'. However, if 'string' is a number generated by mathematical operations, the length of the result is returned. No argument returns the length of $0.
  

  awk 'BEGIN {print length("discombobulation")}'
  16
  awk 'BEGIN {print length(2587946130)}'
  10
  awk 'BEGIN {print length(25 * 2)}'
  2
  awk 'BEGIN {print length(25 * 10 + 1)}'
  3
  awk 'BEGIN{print length (12345) + 1}'
  6
  

• split(string,array [,field separator])
  Divide 'string' into pieces separated by 'field separator' and store them in 'array'.
  

  awk 'BEGIN{n=split("You-are-here!",a,"-");
  print "Array contains " n " elements";
  print "Third element: "a[3]}'
  Array contains 3 elements:
  
  Third element: are
  

  Field separators can be multiple characters

  awk 'BEGIN{n=split("You.:.are.:.here!",a,".:.");
  print "Array contains " n " elements:\n";
  print a[1]a[2]a[3]
  print "Third element: "a[3]"\n"}
  Array contains 3 elements:
  
  Youarehere!
  Third element: here!
  

  You can also pipe a string into awk like this:

  echo "12|23|11" | awk '{split($0,a,"|"); print a[3],a[2],a[1]}'
  11 23 12

  See also Stack Overflow and POFTUT.

• BEGIN
  Executed once only, before the first record (line) is read.
  Example:

  awk 'BEGIN {FS=":"}; {print NF }' names.txt
  2
  2
  2
  2
  2
  2
  

• END
  Executed once only, after all records (lines) have been read.
  Example:

  awk 'END {print FNR}' names.txt
  6