repeat twice each couple of strings in a for cycle

Question

I need to pass to pdftk, a list of arguments constituted by strings repeated twice like:

A1-2 B1-2 A3-4 B3-4 A5-6 B5-6... and so on...

I managed to achieve this with this workaround

for ((x=1, y=2;x>=18, y<=18;x++, y++)); do echo "A$x-$y B$x-$y "; done| awk 'NR %2==1 {print $1, $2} ' | tr '\n' ' '

that gives:

A1-2 B1-2 A3-4 B3-4 A5-6 B5-6 A7-8 B7-8 A9-10 B9-10 A11-12 B11-12 A13-14 B13-14 A15-16 B15-16 A17-18 B17-18

but I'm unsatisfied, and I'm looking for a proper , more elegant and better way to perform this task

Answer 1

for ((x=1; x<=18; x+=2)); do echo -n "A$x-$((x+1)) B$x-$((x+1)) "; done

Answer 2

or even pure awk:

awk 'BEGIN {for (i=1; i<19; i+=2) printf "A"i"-"i+1 " B"i"-"i+1" "}'

Answer 3

With just bash:

pdftk input.pdf cat $(for ((x=1; x<18; x+=2)); do echo {A,B}$x-$((x+1)); done) output output.pdf

With GNU utilities (Linux or Cygwin):

pdftk input.pdf cat $(seq 1 2 17 | awk '{$1 = $1 "-" ($1+1); print "A" $1; print "B" $1}') output output.pdf

With Perl:

pdftk input.pdf cat $(perl -e 'print map {"A$_ B$_ "} map {(2*$_-1) . "-" . (2*$_)} (1..9)') output output.pdf