modifying specific lines a file

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# 1  
Old 07-30-2009
modifying specific lines a file

I need to modify entire file starting from the 3 line. file looks like this
filename : exp

first line

also i have to replace the third content from 3 line by a counter . so the output should look like this:

first line

here 1, 2 is a type of incrementing counter ...

please help Smilie
# 2  
Old 07-30-2009
awk -F, '{x=x+1} {print $1","$2","x","$4}' file

# 3  
Old 07-30-2009
nawk 'BEGIN{n=1;OFS=FS=","}NR>=3{$3=sprintf("\"%s\"",n);n++;print;}'

# 4  
Old 07-30-2009
awk -F, '{x=x+1} {print $1","$2","x","$4}'

This gives output :
first line,,1, second,,2,

it alters first 2 lines as well...

---------- Post updated at 05:42 AM ---------- Previous update was at 05:38 AM ----------

Originally Posted by summer_cherry
nawk 'BEGIN{n=1;OFS=FS=","}NR>=3{$3=sprintf("\"%s\"",n);n++;print;}'

the first 2 lines got missed out ...



i have tried replacing the 3 column with sed and awk .. its working ...
my problem boils down to

how to copy first 2 lines of a file and only alter the remaining lines 3rd column ? i have to store this modified file in some other file ....
# 5  
Old 07-30-2009
This should do the trick:

awk -F, 'NR>2{$3="\042"++c"\042"}1' OFS="," file

# 6  
Old 07-30-2009
will this work?

awk -F, 'NR<3 {print $0}; NR>=3 {x=x+1; print $1","$2","x","$4}' <file>

# 7  
Old 07-30-2009

first line

i think it will work .. but can make me understand the logic ?

---------- Post updated at 06:01 AM ---------- Previous update was at 05:59 AM ----------

also the file i m using , i m not certain of the number of fields it will have ... i mean it is not necessarily 4 ...
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