Change order

Shell Programming and Scripting
1

Good evening
I have a file as below and want to change the order, as in the second column, sed awk Pearl
Thanks

aaaaaaaaaa
bbbbbbbbb
cccccccc
aaaaaaaaaa
bbbbbbbbb
cccccccc

aaaaaaaaaa
cccccccc
bbbbbbbbb
aaaaaaaaaa
cccccccc
bbbbbbbbb
2

Is this what you mean:

awk '(NR%3)==2{p=$0; getline; $0=$0 RS p}1' infile

output:

aaaaaaaaaa
cccccccc
bbbbbbbbb
aaaaaaaaaa
cccccccc
bbbbbbbbb
1 Like
3

I'd first split the file after every 3 lines, like so:

split -l3 file

In this case 2 files are produced: xaa xab

for i in x*; do
awk 'NR == 1 { l1=$0 }
     NR == 2 { l2=$0 }
     NR == 3 { print l1; print $0; print l2}' "$i"
done
1 Like
4

Hi.

Similar to that of Scrutinizer, but more explicit, and slightly less efficient (more division operations involving NR), but still a single pass over the data:

#!/usr/bin/env bash

# @(#) s1	Demonstrate reversal of lines 2 and 3 of trios.

# Infrastructure details, environment, commands for forum posts. 
# Uncomment export command to run script as external user.
# export PATH="/usr/local/bin:/usr/bin:/bin"
set +o nounset
pe() { for i;do printf "%s" "$i";done; printf "\n"; }
pl() { pe;pe "-----" ;pe "$*"; }
LC_ALL=C ; LANG=C ; export LC_ALL LANG
pe ; pe "Environment: LC_ALL = $LC_ALL, LANG = $LANG"
pe "(Versions displayed with local utility \"version\")"
c=$( ps | grep $$ | awk '{print $NF}' )
version >/dev/null 2>&1 && s=$(_eat $0 $1) || s=""
[ "$c" = "$s" ] && p="$s" || p="$c"
version >/dev/null 2>&1 && version "=o" $p printf awk
set -o nounset
pe

FILE=${1-data1}

# Display sample of data file, with head & tail as a last resort.
pe " || start [ first:middle:last ]"
specimen $FILE \
|| { pe "(head/tail)"; head -n 5 $FILE; pe " ||"; tail -n 5 $FILE; }
pe " || end"

pl " Results:"
awk '
(NR % 3) == 1 { print ; next }
(NR % 3) == 2 { hold = $0; next }
              { print ; print hold }
' $FILE |
tee t1

# Check results.

pl " Comparison with desired results:"
if [ ! -f expected-output.txt -o ! -s expected-output.txt ]
then
  pe " Comparison file \"expected-output.txt\" zero-length or missing."
  exit
fi
if cmp expected-output.txt t1
then
  pe " Passed -- files have same content."
else
  pe " Failed -- files not identical -- detailed comparison follows."
  if diff -b expected-output.txt t1
  then
    pe " Passed by ignoring whitespace differences."
  fi
fi

exit 0

producing:

% ./s1

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]
GNU Awk 3.1.5

 || start [ first:middle:last ]
Whole: 5:0:5 of 6 lines in file "data1"
aaaaaaaaaa
bbbbbbbbb
cccccccc
aaaaaaaaaa
bbbbbbbbb
cccccccc
 || end

-----
 Results:
aaaaaaaaaa
cccccccc
bbbbbbbbb
aaaaaaaaaa
cccccccc
bbbbbbbbb

-----
 Comparison with desired results:
 Passed -- files have same content.

cheers, drl

1 Like
5 
sed -n 'p;n;h;n;p;g;p'
1 Like
6

There is always a solution to this the forum:b:

Thanks to everyone

7

Nice...

1 Like
8

Could you please explain me how does it works.

9

sed starts reading on line 1, the -n option suppresses automatic printing.

p: print the current (first) line
n: read the second line
h: do not print that line but put it into hold space
n: read the third line
p: print the third line
g: now get the second line that was stored in hold space
p: print that second line

After that sed starts reading line 4 and the cycle repeats

S.

2 Likes