Question about awk command

ETC Homework & Coursework Questions
1

hi gurus,

I am not sure what the below commands does.

 
awk 'BEGIN {sum=0} {sum=sum+$5} END {print sum}' input_file
2

Hello ramkumar15,

Following may help you in same.

awk '
BEGIN {sum=0} ## In begining sum variable is set to 0
{sum=sum+$5}  ## Now adding $5 values each time with it's previous values so that we can get complete SUM of $5 in variable sum
END {print sum}' input_file  ## At last printing value of variable sum

Thanks,
R. Singh

3 
awk '   # Run awk with the following script...
BEGIN {
               # variable sum is set with a value 0
               sum=0      
} 

# File reading starts from here, read line by line...

{

  # You can also use sum+=$5 it is just a shorthand/shortcut
  # What below expression does is that it first adds the value stored in variable sum to column5 value from your file,
  # and then stores the total of the two back to the variable sum

  sum=sum+$5   

} 


END{
       # After all lines have been read from all input files given to
       # this invocation of awk, run the commands in this section.

      # Finally print sum here
      print sum
}
 ' input_file  # End the script and specify the input file(s) to be processed by this
4

This is progammed utmost meticulously, which is good practice and not a bad thing in the first place. but, using some awk - features, it could be boiled down to

awk '{sum+=$5} END {print sum}' input_file

Any awk variable is allocated on first reference and defaults to zero/empty, so the BEGIN section is superfluous. The += is the addition assignment known from e.g. C .

5

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