awk help!

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# 1  
Old 12-01-2007
Error awk help!

Hey I've just been recently introduced to bash.... well actually unix let alone bash. I'm having a problem with an awk statement:

unit1=$(grep "$cap1" convert.table | awk -F"\t" '{$NF="" ; print $0}' | awk -F"\t" '{$NF="" ; print $0}' | awk -F" " '{if (NF == 4) print $1, $2, $3} ; {if (NF == 3) {print $1, $2} ; {if (NF == 2 ) print $2}')

The problem lies in the third awk statement; I'm trying to see how many fields exist on the current line and print the data accordingly. If theres 4 fields of data I just want the first 3 fields to be printed, etc.

Any help would be greatly appreciated, thanks Smilie Smilie
# 2  
Old 12-02-2007
Try the following for the third awk statement:

awk -F" " '{ if (NF == 4) print $1, $2, $3; if (NF == 3) print $1, $2; if (NF == 2) print $2 }'

# 3  
Old 12-02-2007

I've tried that already and got the following message:

awk: (FILENAME=- FNR=1) fatal: division by zero attempted

?? I'm really lost here because even if i shave the last two "if" statements off, I still get the error but can't seem to figure out the problem Smilie
# 4  
Old 12-02-2007
Give a sample of the input file and the output you desire, perhaps you can do the job with one awk statement.

# 5  
Old 12-02-2007
You didn't say what the problem was. This code looks OK to me:

# echo 123 | awk '{if(NF==2) print};{if(NF==1)print}'
# echo 123 456 | awk '{if(NF==2) print};{if(NF==1)print}'
123 456
# echo 123 456 789| awk '{if(NF==2) print};{if(NF==1)print}'

It looks like you have tab-delimited data AND space-delimited data, and therefore what you're trying is:

"If the line ends in two consecutive tabs (making the last field and next-to-last field empty) then parse the first field by spaces. With 4 words, print the first three; with 3 words, print the first two; with two words, print only the last."

That's a really weird way to parse. Maybe you could post some same input data and a sample of your desired output?

And yes, you should be able to this this with one awk statement. You don't even need the grep:

awk -v PAT="$cap1" '{if ($0~PAT) print}' convert.table
awk '/'$cap1'/{print}' convert.table

Last edited by gus2000; 12-02-2007 at 05:38 PM..
# 6  
Old 12-02-2007

Smilie Ok it works now, the problem was the second awk statement... since it gets rid of the second last field, the grep wasn't finding a pattern (because the pattern lied in the second last field) so I just tweaked it like so:

unit1=$(grep "$convert1" /home/ashamon/asgm2/chinballz/convert.table | awk -F"\t" '{$NF="";print $0}' | awk -F" " '{ if (NF == 5) print $4 ; if (NF == 4) print $3 ; if (NF == 3) print $2 }' 2> /dev/null)

Thanks alot guys, I really appreciate the help, and your responses were pretty quick Smilie have a good one Smilie
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