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Shell Programming and Scripting

Some Awk Getline help?

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Top Forums Shell Programming and Scripting Some Awk Getline help?
# 8  
Old 06-02-2010
Perhaps you are looking for something a bit like this? This would probably limit the searching:
Code:
awk '$3!=f{close(f);f=$3;n=0}{while(!p && getline x<f) if(++n==$2){p=1};print x;p=0}' subset.txt

This will open and close only those files that are specified in subset.txt and look for the right line number and print the record it finds on that line. For efficiency reasons subset.txt would best be sorted..

Output:
Code:
rs10001 900 900 100 100
rs10004 999 121 232 434

Last edited by Scrutinizer; 06-02-2010 at 04:12 PM.. Reason: "!p" and "getline x<f" meeded to be reversed
# 9  
Old 06-02-2010
Create a file with the desired serial# with the name file:
Code:
$ cat file
rs10001
rs10004

Now you can run this command in the directory with the files:
Code:
awk  '
NR==FNR{
  a[$1]=$1
  next
}
a[$1] {row[$1]=$2; file[$1]=$3}
END{
  for(i in file){
    c=0
    while((getline < file[i]) > 0) {
      ++c
      if(c==row[i]) {
        print
      }
    }
  }
}' file masterfile

# 10  
Old 06-02-2010
hmm..it's interesting but it is bringing up a syntax error but doesnt say exactly... I cut and paste directly. Any thoughts?

Thanks

---------- Post updated at 03:56 PM ---------- Previous update was at 03:34 PM ----------

It doesn't like the while (!p &&.....)
it keeps saying that p: event not found
# 11  
Old 06-02-2010
That is a bash message. It typically means that quoting is not done right and bash interprets the "!" . Did you use the single quotes?
# 12  
Old 06-02-2010
I tried single and double quotes around the entire awk statement and they both returned the same error. Should I put the quotes elsewhere?

here is the code I tried:

Code:
awk '$3!=f{close(f);f=$3;n=0}{while(!p && getline x<f ) if(++n==$2){p=1};print x; p=0   }' testfile

Incidentally, what intuitively is meant by while (!p && getline x<f)

I understand the second part to mean "as long getline returns an actual line from file 'f' "
but I'm not understanding where the 'p' comes in. I see the downstream code for 'p' but it still isn't sinking in.


Last edited by Scott; 06-02-2010 at 06:23 PM.. Reason: Please use code tags
# 13  
Old 06-02-2010
Strange. Are you on Solaris? If so use nawk or /usr/xpg4/bin/awk instead of standard awk.

It means while the variable p is empty or zero AND reading a line was successful (in other words no EOF was encountered). If the variable p equals 0 then !p equals 1 (i.e. "TRUE")
This User Gave Thanks to Scrutinizer For This Post:
jeeplou
# 14  
Old 06-02-2010
it worked great and fast! But instead of !p, I used p==0. Do you see any nasty side effects of doing that workaround?
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