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Check for null values in a column

 
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# 8  
Old 04-03-2009
Quote:
Originally Posted by nephros
Which does the exact same thing unless I'm missing something.
[...]
Is there an awk implementation/version that supports that syntax?
I mean:

Code:
awk 'FS="," { ... }'

Last edited by radoulov; 04-03-2009 at 11:18 AM..
# 9  
Old 04-03-2009
Quote:
Originally Posted by radoulov
Is there an awk implementation/version that supports that syntax?
I mean:

Code:
awk 'FS="," { ... }'

/usr/bin/nawk from Solaris 10.
# 10  
Old 04-03-2009
Quote:
Originally Posted by nephros
/usr/bin/nawk from Solaris 10.
the Solaris' '/usr/xpg4/bin/awk' takes this as well:
Code:
/usr/xpg4/bin/awk 'FS="," {if ($8 == "") print "Line", NR, "REJECTED" }' file

but it does not return anything. Reevaluating the whole record [$0=$0] does not help either.
I don't understand why though: the [FS=","] is the condition which after the assignment should evaluate to 'true' and then the following action [{if ...}] should be executed.
But it looks like the the assignment [FS=","] returns 'false' and the 'action' never executes and no 'print' get executed:
Code:
/usr/xpg4/bin/awk 'FS="," {print $0;if ($8 == "") print "Line", NR, "REJECTED" }'

Weird.......
# 11  
Old 04-03-2009
Quote:
Originally Posted by nephros
/usr/bin/nawk from Solaris 10.
Thank you!
When I read your post I did a quick test with the bell-labs awk compiled on Linux
(I thought it was quite similar to the New awk shipped with Solaris) and, as Franklin52 pointed out,
you need to force the recompilation of the current record to get the desired result.

GNU awk and mawk behave the same.

And I confirm that the New awk (/usr/bin/nawk) shipped with Solaris and awk (New awk) on HP-UX recognize it (no recompilation of the current record is needed).

The X-Open POSIX Group awk (/usr/xpg4/bin/awk on Solaris) ignores it silently. The plain old awk (/bin/awk on Solaris) complains with an error.

Solaris:

Code:
% uname -r
5.8
% awk 'FS="," { print $2 }'<<<'a,b 
c,d'
awk: syntax error near line 1
awk: bailing out near line 1
% nawk 'FS="," { print $2 }'<<<'a,b 
c,d'
b
d
% /usr/xpg4/bin/awk 'FS="," { print $2 }'<<<'a,b 
c,d'
%

Linux:

Code:
% newawk 'FS="," { print $2 }'<<<'a,b
c,d'

d
% gawk 'FS="," { print $2 }'<<<'a,b
c,d'

d
% mawk 'FS="," { print $2 }'<<<'a,b
c,d'

d

Last edited by radoulov; 04-03-2009 at 11:55 AM..
# 12  
Old 04-06-2009
Quote:
Originally Posted by Franklin52
You are missing something...Smilie
The FS is changed after the line is read, so it doesn't affect the FS in the current line in the buffer. Your solution gives all the lines of the data from the OP. To get the proper output you have to rearrange the buffer with $0=$0:

Code:
nawk '{FS=",";$0=$0;if ($8 == "") print "Line", NR, "REJECTED" }' file

Regards
Guys Thanks for the clarifications on awk n nawk.Guys you all are opening the file and reading it line by line.But how do i check whether a particular column contains atleast one NULL column without reading the file line by line..Thats my requisite.Smilie
# 13  
Old 04-06-2009
Quote:
Originally Posted by ganesh_248
Guys Thanks for the clarifications on awk n nawk.Guys you all are opening the file and reading it line by line.But how do i check whether a particular column contains atleast one NULL column without reading the file line by line..Thats my requisite.Smilie
all test unix commands like grep ,sed awk etc etc.. work on line you will get very very few commands in unix which act on full file at once so if you find any let me knowSmilie
# 14  
Old 04-06-2009
Bug
Quote:
Originally Posted by vidyadhar85
all test unix commands like grep ,sed awk etc etc.. work on line you will get very very few commands in unix which act on full file at once so if you find any let me knowSmilie
Vidyadar,i can read line by line and check whether the particular column has NULL or NOT.But i receive Huge files and they come in batches of 100's.so opening each and every file and reading it line by line consumes lot of time.I am trying out if there is any other possibility to create a shell script that is efficient and less time consuming for this problem.:-)
Please do let me know if u find any command bro' .
 
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