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Replace string in a file with some content indexed from another file.

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# 1  
Old 06-21-2014
Replace string in a file with some content indexed from another file.
We have two files

file 1: (usually small, ~100 lines), each line contains a : separated index, value e.g

Code:
2: Apple
1: Banana
5: Pear
7: Orange

File 2: (usually large, 10 million lines or more), each line contains a single string value. e.g
Code:
xyz1
xyz2
xyz3
xyz4
xyz5
xyz6
xyz7

Now the goal is to replace the "index" in the first file (in place) with the value from the second file. i.e. the index in the first file is the line number to be used to get the value from the second file.

e.g the contents for file 1 should be
Code:
xyz2:Apple
xyz1: Banana
xyz5: Pear
xyz7: Orange

Last edited by Don Cragun; 06-21-2014 at 06:22 PM.. Reason: Add CODE tags.
# 2  
Old 06-21-2014
Try something like this:
Code:
awk 'NR==FNR{A[$1]=$2; next} FNR in A{print $1, A[FNR]}' FS=": *" file1 FS=" " OFS=: file2 > newfile

If succesful replace file1 with newfile.

Output:
Code:
xyz1:Banana
xyz2:Apple
xyz5:Pear
xyz7:Orange

These 2 Users Gave Thanks to Scrutinizer For This Post:
AlokKumbhare RavinderSingh13
# 3  
Old 06-21-2014
If preserving the order of lines in File 1 is important, this comes close to producing the output you requested:
Code:
awk '
BEGIN {	# Set input and output field separators
	FS = OFS = ":"
}
NR == 1 {
	# Save 1st input file pathname (since we will overwrite it later)
	f1name = FILENAME
}
NR == FNR {
	# Gather data from 1st input file
	d[++f1c] = $2	# Data to be saved.
	l[$1] = f1c	# Line # from 2nd file to be printed on Line # from
			# 1st file.
	next
}
FNR in l {
	# Gather data from 2nd input file for any line specifeid in the 1st
	# field in the 1st file.
	o[l[FNR]] = $1
}
END {	# Overwrite the 1st input file with data gathered from both input files.
	for(i = 1; i <= f1c; i++)
		print o[i], d[i] > f1name
}' "File "[12]

which, with the sample input files you provided, changes the contents of File 1to be:
Code:
xyz2: Apple
xyz1: Banana
xyz5: Pear
xyz7: Orange

Be sure that you have a backup copy of File 1 before trying this since this script overwrites it.

If you want to try this on a Solaris/SunOS system, change awk to /usr/xpg4/bin/awk, /usr/xpg6/bin/awk, or nawk.
This User Gave Thanks to Don Cragun For This Post:
AlokKumbhare
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