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Reversing numbers in a datafile of rows and columns

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# 1  
Old 04-08-2009
Reversing numbers in a datafile of rows and columns
Hello,

I've tried searching the forum for an answer to my question, but without any luck...

I have a datafile looking simplified as follows:
01 02 03 04 05 06
07 08 09 10 11 12
13 14 15 16 17 18
19 20 21 22 23 24

I want to reverse it by rearranging all the numbers from last to first, so that it looks like this:
24 23 22 21 20 19
18 17 16 15 14 13
12 11 10 09 08 07
06 05 04 03 02 01

I've tried using tac:
Code:
> tac --separator=" " filename
24
23 22 21 20 18
19 17 16 15 14 12
13 11 10 09 08 06
07 05 04 03 02 01

This does not give me the result I want. Can anyone explain why?

Maybe I should use sed or awk, or something else? Can anyone help me with this one?
# 2  
Old 04-08-2009
nawk -f invert.awk myFile

invert.awk:
Code:
{
  for(i=1; i<=NF;i++)
    arr[FNR,i]=$i
  nf=NF
  fnr=FNR
}
END {
  for(i=fnr; i;i--)
    for(j=nf; j;j--)
      printf("%s%c", arr[i,j], (j==1)?ORS:OFS)
}

# 3  
Old 04-08-2009
Code:
# tac file | while read line;do echo $line|tr " " "\n"|sort -rn|tr "\n" " ";echo; done
24 23 22 21 20 19
18 17 16 15 14 13
12 11 10 09 08 07
06 05 04 03 02 01

# 4  
Old 04-08-2009
Hi.

The original tac reverses tokens separated by spaces. The last token on each line is "number-followed-by-newline". When the tokens are reversed, the last token is "24-newline", and so on.

The solutions posted are fine. Here is a compact perl solution:
Code:
#!/usr/bin/env bash

# @(#) s1       Demonstrate reversal of symbols on lines (perl).

echo
set +o nounset
LC_ALL=C ; LANG=C ; export LC_ALL LANG
echo "Environment: LC_ALL = $LC_ALL, LANG = $LANG"
echo "(Versions displayed with local utility \"version\")"
version >/dev/null 2>&1 && version "=o" $(_eat $0 $1) tac perl
set -o nounset
echo

FILE=${1-data1}

echo " Data file $FILE:"
cat $FILE

echo
echo " Original results (trailing newline added):"
tac --separator=" " $FILE
echo

echo
echo " Re-written results:"
tac $FILE |
perl -n -e 'chomp;print join(" ",reverse(split(/ /))),"\n";'

exit 0

producing:
Code:
% ./s1

Environment: LC_ALL = C, LANG = C
(Versions displayed with local utility "version")
OS, ker|rel, machine: Linux, 2.6.11-x1, i686
Distribution        : Xandros Desktop 3.0.3 Business
GNU bash 2.05b.0
tac (coreutils) 5.2.1
perl 5.8.4

 Data file data1:
01 02 03 04 05 06
07 08 09 10 11 12
13 14 15 16 17 18
19 20 21 22 23 24

 Original results (trailing newline added):
24
23 22 21 20 18
19 17 16 15 14 12
13 11 10 09 08 06
07 05 04 03 02 01

 Re-written results:
24 23 22 21 20 19
18 17 16 15 14 13
12 11 10 09 08 07
06 05 04 03 02 01

The heart of the operation: after the lines are reversed by tac, process them with a perl script. The easy-to-read-but-not-so-easy-to-understand perl code stacks a number of functions: split the line into an array of tokens, reverse the content of the array (and thus the tokens), join the array with a space as separator into a string, print the string with a newline at the end. The "-n" says to do that series of operations for each line ... cheers, drl
# 5  
Old 04-14-2009
Quote:
Originally Posted by vgersh99
nawk -f invert.awk myFile

invert.awk:
Code:
{
  for(i=1; i<=NF;i++)
    arr[FNR,i]=$i
  nf=NF
  fnr=FNR
}
END {
  for(i=fnr; i;i--)
    for(j=nf; j;j--)
      printf("%s%c", arr[i,j], (j==1)?ORS:OFS)
}

This code does exactly the job I was looking for. Thanks a lot!
But I noticed a little problem when I tried it on one of my datafiles.

The datafile looks simplified as:
01 02 03 04 05 06
07 08 09 10 11 12
13 14 15 16 17 18
19 20 21 22 23 24
25 26 27 28 29 30
31 32 33

When I used the code, it produced:
33 32 31
27 26 25
21 20 19
15 14 13
09 08 07
03 02 01

I want it to produce:
33 32 31 30 29 28
27 26 25 24 23 22
21 20 19 18 17 16
15 14 13 12 11 10
09 08 07 06 05 04
03 02 01

Is there an easy way around this problem by modifying this code?
# 6  
Old 04-14-2009
Quote:
Originally Posted by ghostdog74
Code:
# tac file | while read line;do echo $line|tr " " "\n"|sort -rn|tr "\n" " ";echo; done
24 23 22 21 20 19
18 17 16 15 14 13
12 11 10 09 08 07
06 05 04 03 02 01

Hi,

# tac file | awk '{print $6,$5,$4,$3,$2,$1}'

Any loopholes in the above command?
Hope this suites this situation. Smilie
# 7  
Old 04-14-2009
Quote:
Originally Posted by reddybs
Hi,

# tac file | awk '{print $6,$5,$4,$3,$2,$1}'

Any loopholes in the above command?
Hope this suites this situation. Smilie
should be alright if the file has exactly six fields. If the fields are variable, then might not be suitable.
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