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Top Forums Shell Programming and Scripting Get the MAX value out of a column Post 302798617 by alister on Thursday 25th of April 2013 12:33:42 AM
Old 04-25-2013
While the OP's sample data consists exclusively of positive integers, if negative values and zeroes must be handled, neither solution is correct.

Corona's code will unconditionally set MAX to the next line's $3, if MAX is ever set to 0.
Code:
$ cat file
-1 -1 -1 -1
0 0 0 0
-2 -2 -2 -2
$ awk 'NR==FNR { if((!MAX)||(MAX<$3)) MAX=$3; next }; $3==MAX' file file
-2 -2 -2 -2
$ awk 'NR==FNR { if((NR==1)||(MAX<$3)) MAX=$3; next }; $3==MAX' file file
0 0 0 0

Yoda's code implicitly uses a max of 0 when NR==1 (a numeric 0 is the default value of an uninitialized variable). If that implicit 0, which is not present in the file, is greater than all values, B[2]==max will never succeed and no output is generated. max must be initialized from the first value of $3.
Code:
$ cat file
-1 -1 -1 -1
-2 -2 -2 -2
-3 -3 -3 -3
$ awk '{A[NR" "$3]=$0;max=max<$3?$3:max}END{for(k in A){split(k,B);if(B[2]==max) print A[k]}}' f
$ awk '{A[NR" "$3]=$0;max=max<$3||NR==1?$3:max}END{for(k in A){split(k,B);if(B[2]==max) print A[k]}}' f
-1 -1 -1 -1

Regards,
Alister
 

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IGAWK(1)							 Utility Commands							  IGAWK(1)

NAME
igawk - gawk with include files SYNOPSIS
igawk [ all gawk options ] -f program-file [ -- ] file ... igawk [ all gawk options ] [ -- ] program-text file ... DESCRIPTION
Igawk is a simple shell script that adds the ability to have ``include files'' to gawk(1). AWK programs for igawk are the same as for gawk, except that, in addition, you may have lines like @include getopt.awk in your program to include the file getopt.awk from either the current directory or one of the other directories in the search path. OPTIONS
See gawk(1) for a full description of the AWK language and the options that gawk supports. EXAMPLES
cat << EOF > test.awk @include getopt.awk BEGIN { while (getopt(ARGC, ARGV, "am:q") != -1) ... } EOF igawk -f test.awk SEE ALSO
gawk(1) Effective AWK Programming, Edition 1.0, published by the Free Software Foundation, 1995. AUTHOR
Arnold Robbins (arnold@skeeve.com). Free Software Foundation Nov 3 1999 IGAWK(1)
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