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awk to insert new line conditionally

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# 1  
Old 01-31-2013
awk to insert new line conditionally
Dear All,

I have a file like:

Quote:
1 1 1 2011
2 2 2 2001
3 3 3 2011
4 4 4 2001
5 5 5 2011
If $4=2001, a duplicated line will be inserted and $4 will be assigned value 2011; so that the new file would be:

Quote:
1 1 1 2011
2 2 2 2001
2 2 2 2011
3 3 3 2011
4 4 4 2001
4 4 4 2011
5 5 5 2011
How to write awk to accomplish this? thank you very much!
# 2  
Old 01-31-2013
try:
Code:
awk '1;$4==2001 {$4=2011; print}' infile

or
Code:
awk '1;$4==x {$4=y; print }' x=2001 y=2011 infile

or
Code:
sed -n 'p;/2001$/s/2001$/2011/p' infile

Last edited by rdrtx1; 01-31-2013 at 05:50 PM.. Reason: fixed. (copied from wrong buffer)
This User Gave Thanks to rdrtx1 For This Post:
littlewenwen
# 3  
Old 01-31-2013
Code:
awk '$4==2001{d=$0;sub("2001","2011",d);print $0;print d;}$4!=2001{print}' filename

This User Gave Thanks to Yoda For This Post:
littlewenwen
# 4  
Old 01-31-2013
Thank you very much.
By the way what does "1" means in
awk '1;.......}' infile
# 5  
Old 01-31-2013
1 = true = print (in awk)
This User Gave Thanks to rdrtx1 For This Post:
littlewenwen
# 6  
Old 01-31-2013
Code:
awk '1;$4==2001 && $4=2011'  myFile

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