Replace a numeric values in a certain column

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# 1  
Replace a numeric values in a certain column

Hi All,

I am trying to replace a certain value from one place in a file . In the below file at position 35 I will have 8 I need to modify all 8 in that position to 7

I tried
awk '{gsub("8","7",$35)}1' infile > outfile  ----> not working 
sed -i 's/8/7'g' infile --- it is replacing all the values  to 7 in the file.


Expected output:


Also on a follow up if I want to replace 008 to 009 . 008 is on the same column 33-35. What should I do

Last edited by arunkumar_mca; 02-20-2019 at 11:18 PM..
# 2  
Hello arunkumar_mca,

Could you please try following once. This is specifically for 35th character's replacement.
I am using substring function of awk to get first 34 characters and then printing 7 along with rest of the characters of line.

awk '{print substr($0,1,34) "7" substr($0,36)}'  Input_file

R. Singh
# 3  
Originally Posted by arunkumar_mca
Hi All,
Also on a follow up if I want to replace 008 to 009 . 008 is on the same column 33-35. What should I do
Hello arunkumar_mca,

Position of a character(s) is different from column number.

In above example if you talk in normal terms then position of a is 7 and it is NOT 7th column in that line.

Now question is when it becomes 7th column, let us think by default field separator is SPACE(I am talking about awk here). So your 7th position will be "called as " 7th field/column when field delimiter of awk is been set to NULL. Which is again a GNU awk function only. So please clear in your statements here.

R. Singh

Last edited by RavinderSingh13; 02-21-2019 at 12:56 AM..
# 4  
Note that the code RavinderSingh13 suggested in post #2 in this thread will change the 35th character on every line; not just on lines where the original character in that position was "8".

For your second question you might want to try:
awk '
{	if(substr($0, 33, 3) == "008")
		print substr($0, 1, 32) "009" substr($0, 36)
	else	print
}' infile > outfile

It wasn't at all clear whether you wanted to make both changes in the same input file. If you do, the order in which you process the changes is very important. If you perform the two operations in the order you specified, the change of "008" to "009" will never happen since the "8" will already have been changed to a "7".

If what you want is to change "008" in character positions 33 through 35 (with the first position on a line being character position 1) and if there is a "8" in character position 35 where at least one of the characters in positions 33 and 34 is not "0", then you might want to try:
awk '
{	if(substr($0, 33, 3) == "008")
		print substr($0, 1, 32) "009" substr($0, 36)
	else	if(substr($0, 35, 1) == "8")
			print substr($0, 1, 34) "7" substr($0, 36)
		else	print
}' infile > outfile

And, as RavinderSingh13 already said, you need to tell us on every thread that you start what operating system and shell you're using. Both of the above scripts will work on most BSD, Linux, and UNIX operating systems, but will not work on Solaris/SunOS systems. On Solaris/SunOS systems, you'll need to change awk in both of the above scripts to either /usr/xpg4/bin/awk or nawk.

Last edited by Don Cragun; 05-21-2019 at 03:04 PM.. Reason: Fix tags on nawk: s/CODE/ICODE/g.
This User Gave Thanks to Don Cragun For This Post:
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