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Old 05-20-2008, 09:39 PM   #1
skuz_ball
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Registered: Nov 2007
Location: Melbourne, Australia
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adding constant (number) to a number in all rows


Hi all,

I have a file which has temperatures in Kelvin in a column and would like to convert these numbers to Celsius. I think sed would be appropriate to use in this instance but having multiple lines in the file has confused me a bit. im trying to do this in a shell script. I usually use ksh to do this work but am open to any suggestions.

eg file1:

1 2 3 4
1 2 3 5
1 2 3 3
1 2 3 7

Would like to take away 3 from last column so file2 looks like this:

1 2 3 1
1 2 3 2
1 2 3 0
1 2 3 4

Any help would be greatly apprciated.
 
Old 05-20-2008, 10:46 PM   #2
jlinkels
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Registered: Oct 2003
Location: Bonaire
Distribution: Debian Wheezy/Jessie/Sid, Linux Mint DE
Posts: 4,234

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awk is your friend.

Code:
cat file1 | awk '{print $1 " " $2 " " $3 " "  $4 + 273}' > file2

That is how to convert Celsius to Kelvin. I don't understand your last conversion to take 3 away from the last column.

In sed it would be:

Code:
sed s/3\ *$/0/
jlinkels
 
Old 05-20-2008, 10:57 PM   #3
rlhartmann
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Registered: Mar 2008
Posts: 73

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Here's a perl script to do it:

Quote:
#!/usr/bin/perl
while(<STDIN>) # Read from stdin
{

chomp;
@columns=split(/\s/,$_);
$columns[3]-=3;
$string=join("\t",@columns); # separate with tab
print("$string\n");
}
Give it execute permissions, and run using:
[B]./kelvin.pl < datafile >outputfile
 
  


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