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Insert string 'NULL' where there is a null value

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# 1  
Old 05-27-2010
Insert string 'NULL' where there is a null value
I have an input file having 7 fields delimited by ,
eg :
Code:
1,ABC,hg,1,2,34,3
2,hj,YU,2,3,4,
3,JU,kl,4,5,7,
4,JK,KJ,3,56,4,5

The seventh field here in some lines is empty, whereas the other lines there is a value.
How do I insert string NULL at this location (7th loc) for these lines where output will look like
Code:
1,ABC,hg,1,2,34,3
2,hj,YU,2,3,4,NULL
3,JU,kl,4,5,7,NULL
4,JK,KJ,3,56,4,5

Last edited by Franklin52; 05-27-2010 at 08:32 AM.. Reason: Please use code tags!
# 2  
Old 05-27-2010
One way:
Code:
awk -F, '!$7{$7="NULL"}1' OFS="," file

This User Gave Thanks to Franklin52 For This Post:
zilch
# 3  
Old 05-27-2010
Hello Franklin,

could you explain the meaning of the number "one"?
I suppose that is for printing the line...but which is the meaning exactly?

thank you
# 4  
Old 05-27-2010
for the last column:

Code:
sed 's/,$/,NULL/g' file

to insert a "NULL" in every empty column:

Code:
sed -e 's/,,/,NULL,/g' -e 's/,$/,NULL/g' file

# 5  
Old 05-27-2010
wow, the sed works great. Exactly what i wanted. I was stuck with 's/$\x0/NULL/g' and was wondering what was the mistake. Well thank you very much funksen
# 6  
Old 05-27-2010
Quote:
Originally Posted by albertogarcia
Hello Franklin,

could you explain the meaning of the number "one"?
I suppose that is for printing the line...but which is the meaning exactly?

thank you
Hi,

The 1 is a condition without any action. It matches when its value is nonzero (if a number) or non-null (if a string).
If it's true awk prints the current record, similar to {print}.

Regards
# 7  
Old 05-27-2010
Quote:
It matches when its value is nonzero (if a number) or non-null (if a string).
How do we get to know whether its true or not? is there any dependency with the previous command/expression written just before "1" ?
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