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# 1  
Old 12-11-2014
Add comment if not present
I have a file

Code:
cat /root/file
#import node1
#import node2
import node2
import node4

After sed/awk operation the file should be as follows

Code:
cat /root/file
#import node1
#import node2
#import node2
#import node4

I was able to retrieve the #import, but not able to place comment in missing lines.
Code:
[root@server node]# cat /root/file  |  egrep  -o "[^ ]+import"
#import
#import

# 2  
Old 12-11-2014
How about
Code:
sed 's/^[^#]/#&/' file
#import node1
#import node2
#import node2
#import node4

# 3  
Old 12-11-2014
Quote:
After sed/awk operation
Providing a (verbose) awk variant...
Code:
awk '$0 !~ /^#/ { $0="#"$0 } { print }' file

# 4  
Old 12-11-2014
Thanks rubic and junior-helper. How can we insert to file using awk, ie similar to sed -i
# 5  
Old 12-11-2014
Hello anil510,

We can use following command for same.
Code:
sed -i 's/^[^#]/#&/'  Input_file

Thanks,
R. Singh
# 6  
Old 12-11-2014
Quote:
Originally Posted by anil510
How can we insert to file using awk, ie similar to sed -i
Unfortunately, awk has no such option. If you want to use the awk approach, you'll need something like
Code:
awk ... file > file.new
mv file.new file

PS: Under the hood, sed does the same Smilie
# 7  
Old 12-11-2014
Code:
$ awk -F"#" ' NF==1 ? $0="#"$0 : 1 ' file
#import node1
#import node2
#import node2
#import node4
$ awk -F"#" ' $2 ? 1 : $0="#"$0 ' file
#import node1
#import node2
#import node2
#import node4
$ awk ' { sub("^[^#]","#&") } 1 ' file
#import node1
#import node2
#import node2
#import node4

Last edited by anbu23; 12-11-2014 at 09:05 AM..
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