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Split large file based on last digit from a column

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# 8  
Old 05-16-2010
it's the substring in bash
Code:
${<string>:<start>:<length>}

if length is omitted, extracts to end of string like
Code:
${<string>:<start>}

if start is negative, counts from end of string, but it must be in (), like in the given script.
NOTE: first character has index 0.
look there : Manipulating Strings
Last edited by frans; 05-16-2010 at 06:06 AM.. Reason: added link
This User Gave Thanks to frans For This Post:
alain.kazan
# 9  
Old 05-16-2010
Code:
awk -F "" '{print > $NF ".txt"}' urfile

# 10  
Old 05-17-2010
Timing comparison
Hi.

Once I process files above 1M lines, I tend to think in terms of {awk,perl}.

My awk code is about the same as that from rdcwayx -- not as clever as that, however: I used length and index functions.

I whipped up a small timing test framework, and created a 600K line file for comparison and easy arithmetic. These are the results:
Code:
% ./run

 Time for awk script on 600000 lines in file data1:

Environment: LC_ALL = C, LANG = C
(Versions displayed with local utility "version")
OS, ker|rel, machine: Linux, 2.6.26-2-amd64, x86_64
Distribution        : Debian GNU/Linux 5.0 
GNU bash 3.2.39
printf - is a shell builtin [bash]
specimen (local) 1.17
GNU Awk 3.1.5


-----
 || start [ first:middle:last ]
Edges: 5:0:5 of 600000 lines in file "data1"
298138
201666
307112
739965
187303
   ---
347236
113888
869875
958456
384340
 || end

-----
 Results:
 Processed 600000 lines.

-----
 Size of files:
  60250   60250  421750 f0
  59790   59790  418530 f1
  60266   60266  421862 f2
  59764   59764  418348 f3
  60043   60043  420301 f4
  59937   59937  419559 f5
  60029   60029  420203 f6
  59716   59716  418012 f7
  60110   60110  420770 f8
  60095   60095  420665 f9
 600000  600000 4200000 total

real	0m2.616s
user	0m1.820s
sys	0m0.312s

 Timing for shell loop on 600000 lines in file data1:

real	0m28.599s
user	0m15.465s
sys	0m9.269s

 Total number of lines in 10 files: 600000

So for a 60M file, one could estimate the time needed for a production run (on my workstation) by multiplying the times by 100.

The specific awk code was:
Code:
awk '
	{ digit = substr($0,length($0),1) 
	  print $0 > "f"digit
	}
END	{ print " Processed", NR, "lines." }
' $FILE

and the shell loop was:
Code:
while read L
do
    echo $L >> f${L:(-1)}
done < $FILE

Best wishes ... cheers, drl
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