Get the average of lines with the same first 4 letters Post: 303021706

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Top Forums Shell Programming and Scripting Get the average of lines with the same first 4 letters Post 303021706 by Don Cragun on Wednesday 15th of August 2018 09:49:54 AM

08-15-2018

Registered User

Of course my suggested awk script can be turned into a single line of code. But, if you can't do that on your own, there is absolutely no possible way that the 1-liner version of that code will be easier to understand than the version I provided before. Code is always easier to understand if you can see the structure that shows, by indentation, how commands are connected. And, you can't include comments in the middle of an awk 1-liner, so I can't provide you with a commented 1-liner.

Hoping that comments will help you understand what the code is doing, I provide the following:

Code:

awk '	# Invoke awk and start the script specifying actions to be performed.
function print_total() {
	# Define function to print the total acccumulated for the previous set
	# of lines with the same four characters at the start of the 1st field.
	printf("\nTotal Sum of %s: %d\n", last, total)
}
last != substr($1, 1, 4) {
	# Perform the actions in this group when the 1st four characters in the
	# 1st field on this line is not the same as the 1st four characters in
	# the 1st field that we saw on the previous line.  Since there is no
	# previous line when we are reading the 1st line from our input file,
	# we also perform the actions in this group when processing the 1st
	# line in the input file.
	if(NR > 1) {
		# Perform these actions when we are not processing line #1.
		print_total()				# Print the total for
							# for the previous set.
		printf("\n=======================\n")	# Print a set separator.
	}
	# Save the 1st four characters from this line to compare against
	# subsequent input lines.
	last = substr($1, 1, 4)
	# Clear the total for this new set.
	total = 0
}
{	# Perform the actions in this group for every line in the input file.
	print		# Print the current input line.
	total += $2	# Add the contents of the 2nd field on this line to the
			# total for this set.
}
END {	# Perform the actions in this group after we have read the last line of
	# input from the input file.
	print_total()	# Print the total for the last set.
}' hhhh	# End the awk script and name the file to be processed.

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LEARN ABOUT DEBIAN

plan9-join

JOIN(1) 						      General Commands Manual							   JOIN(1)

NAME

       join - relational database operator

SYNOPSIS

       join [ options ] file1 file2

DESCRIPTION

       Join forms, on the standard output, a join of the two relations specified by the lines of file1 and file2.  If one of the file names is the
       standard input is used.

       File1 and file2 must be sorted in increasing ASCII collating sequence on the fields on which they are to be joined, normally the  first	in
       each line.

       There  is  one line in the output for each pair of lines in file1 and file2 that have identical join fields.  The output line normally con-
       sists of the common field, then the rest of the line from file1, then the rest of the line from file2.

       Input fields are normally separated spaces or tabs; output fields by space.  In this case, multiple separators count as	one,  and  leading
       separators are discarded.

       The following options are recognized, with POSIX syntax.

       -a n   In addition to the normal output, produce a line for each unpairable line in file n, where n is 1 or 2.

       -v n   Like -a, omitting output for paired lines.

       -e s   Replace empty output fields by string s.

       -1 m
       -2 m   Join on the mth field of file1 or file2.

       -jn m  Archaic equivalent for -n m.

       -ofields
	      Each  output  line  comprises the designated fields.  The comma-separated field designators are either 0, meaning the join field, or
	      have the form n.m, where n is a file number and m is a field number.  Archaic usage allows separate arguments for field designators.

       -tc    Use character c as the only separator (tab character) on input and output.  Every appearance of c in a line is significant.

EXAMPLES

       sort /etc/passwd | join -t: -1 1 -a 1 -e "" - bdays
	      Add birthdays to the /etc/passwd file, leaving unknown birthdays empty.  The layout of /adm/users is given in passwd(5); bdays  con-
	      tains sorted lines like

       tr : ' ' </etc/passwd | sort -k 3 3 >temp
       join -1 3 -2 3 -o 1.1,2.1 temp temp | awk '$1 < $2'
	      Print all pairs of users with identical userids.

SOURCE

       /src/cmd/join.c

SEE ALSO

       sort(1), comm(1), awk(1)

BUGS

       With default field separation, the collating sequence is that of sort -b -ky,y; with -t, the sequence is that of sort -tx -ky,y.

       One of the files must be randomly accessible.

																	   JOIN(1)

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