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double while

 
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# 1  
Old 02-29-2012
double while
file1 contents:
Code:
jandoe1
johndoe1

file2 contents:
Code:
jandoe
johndoe

my output file names file3, and has contents as:
Code:
This is jandoe1

my script:
Code:
cat file1 | while read line1
cat file2 | while read line2
do
do
   sed -e 's/${line1}/${line2}/g' file3 > file3
done
done

all said and done, my output should look like this: This is jandoe

i just don't how to use double while.
Last edited by Scott; 02-29-2012 at 03:25 PM.. Reason: Use code tags, please...
# 2  
Old 02-29-2012
Code:
exec 3<file2
while read line1; do
  while read line2 <&3; do
   sed "s/${line1}/${line2}/g" file3
  done
done < file1

Output:
Code:
This is jandoe
This is johndoe

You can't write (in the sed part) back to "file3" unless your sed supports the -i option. If it doesn't, you need to write to another (temporary) file, and then copy it over the original.
# 3  
Old 02-29-2012
worked perfectly, but i don't understand:
exec 3<file2
and done < file1

and what is
<&3

and what if file3 has contents:

This is jandoe1
This is johndoe1

my output should look like this:

This is jandoe
This is johndoe
Last edited by lawsongeek; 02-29-2012 at 05:17 PM..
# 4  
Old 02-29-2012
Quote:
Originally Posted by lawsongeek
worked perfectly, but i don't understand:
Code:
exec 3<file2

Open file2 into file descriptor 3, so you can read from file2 in the future by redirecting from fd3 like <&3

Code:
and done < file1

Feed file1 into standard input for that loop only, so read commands etc inside it read from that file.

Code:
and what is 
<&3

file descriptor 3.
Last edited by methyl; 02-29-2012 at 09:51 PM.. Reason: unravel corrupt code tags
# 5  
Old 02-29-2012
Mispost
# 6  
Old 03-01-2012
sorry about that. i will post under shell scripting and programing next one i have issue/question about script. again, sorry and thank you.
 
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