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I have a shell script in which I have defined an array. The array contains more than 2 elements. I need to find the combination of all the elements in my array. Suppose, if my array has the elements, {12345, 56789, 98765}, I am trying to get the output as,

12345, 56789
12345, 98765
56789, 98765

I tried the php code from here.

<?php
function pc_permute($items, $perms = array( )) {
    if (empty($items)) {
        print join(' ', $perms) . "\n";
    }  else {
        for ($i = count($items) - 1; $i >= 0; --$i) {
             $newitems = $items;
             $newperms = $perms;
             list($foo) = array_splice($newitems, $i, 1);
             array_unshift($newperms, $foo);
             pc_permute($newitems, $newperms);
         }
    }
}
pc_permute(split(' ', '12345 56789 98765'));
?>

I get the output as,

12345 56789 98765
56789 12345 98765
12345 98765 56789
98765 12345 56789
56789 98765 12345
98765 56789 12345

Is it possible to get the combination in 2 elements sized output? I am not concerned with the order and so if A B is got as a combination, I do not need the reverse (B A).

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2
  • You seem to be looking for combinations not permutations if order is not material Commented Apr 8, 2014 at 21:39
  • Yeah, I am looking for combinations. I always get confused between those 2 terms :) Commented Apr 8, 2014 at 21:40

2 Answers 2

Reset to default
1

All you need is printf. It's the print function - that's its job.

printf '%s\t%s\n' ${array[@]}

You do it like this:

( set -- 12345 56789 98765; for i ; do 
    eval set -- $(printf '"$%s" ' `seq 2 $#` 1)
    echo "$*"
done )

OUTPUT

56789 98765 12345
98765 12345 56789
12345 56789 98765

I didn't need eval - that was dumb. Here's a better one:

( set -- 12345 56789 98765 ; 
until [ $((i=i+1)) -gt $# ] ; do
    set -- $(s=$1 ; shift ; printf '%s\n' "$@" "$s")
    printf '%s ' "$@" ; echo
done)

OUTPUT

56789 98765 12345
98765 12345 56789
12345 56789 98765

And then if you want only two elements you just change it a little bit - one more line:

( set -- 12345 56789 98765 ;
    until [ $((i=i+1)) -ge $# ] ; do
        set -- $(s=$1 ; shift ; printf '%s\n' "$@" "$s")
        v="${v}$(printf '%s ' "$@")"
    done ; printf "%s\t%s\n" $v
    )

OUTPUT

56789   98765
12345   98765
12345   56789

I do this all of the time, but never the bashisms. I always work with the real shell array so it took a few minutes to get hold of it.

Here's a little script I wrote for another answer:

    abc="a b c d e f g h i j k l m n o p q r s t u v w x y z"
for l in $abc ; do { 
        h= c= ; [ $((i=i+1)) -gt 26 ] && n=$((n+26)) i=
    xyz=$(x=${xyz:-$abc} ;\
        printf %s\\n ${x#?} $l)
    mid=$(set -- $xyz ; eval echo \$$((${#}/4))) ;\
        echo "$mid $l" >&2 ;
        [ $(((i+n)%${mod=3})) -eq 0 ] && c="$mid" h="${xyz%"$mid"*}"
    line="$(printf '%s ' $h $c ${xyz#"$h"})"
    printf "%s$(printf %s ${xyz#?}${mid})\n" \
        ${line} >|/tmp/file$((i+n))
} ; done

This writes to 26 files. They look like this only they increment per file:

bcdefghijklmnopqrstuvwxyzag
ccdefghijklmnopqrstuvwxyzag
dcdefghijklmnopqrstuvwxyzag
ecdefghijklmnopqrstuvwxyzag
fcdefghijklmnopqrstuvwxyzag
gcdefghijklmnopqrstuvwxyzag
hcdefghijklmnopqrstuvwxyzag
icdefghijklmnopqrstuvwxyzag
jcdefghijklmnopqrstuvwxyzag
kcdefghijklmnopqrstuvwxyzag
lcdefghijklmnopqrstuvwxyzag
mcdefghijklmnopqrstuvwxyzag
ncdefghijklmnopqrstuvwxyzag
ocdefghijklmnopqrstuvwxyzag
pcdefghijklmnopqrstuvwxyzag
qcdefghijklmnopqrstuvwxyzag
rcdefghijklmnopqrstuvwxyzag
scdefghijklmnopqrstuvwxyzag
tcdefghijklmnopqrstuvwxyzag
ucdefghijklmnopqrstuvwxyzag
vcdefghijklmnopqrstuvwxyzag
wcdefghijklmnopqrstuvwxyzag
xcdefghijklmnopqrstuvwxyzag
ycdefghijklmnopqrstuvwxyzag
zcdefghijklmnopqrstuvwxyzag
acdefghijklmnopqrstuvwxyzag
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5
  • I need all the combinations. with printf it is just splitting the input into 2 variables and printing. I tried the array array+=(s1 s2 s3 s4 s5 s6 s7). Commented Apr 9, 2014 at 1:32
  • Ok. So printf printf. Commented Apr 9, 2014 at 1:33
  • Nopes. It is not working. Commented Apr 9, 2014 at 1:37
  • @Ramesh - it does now, though at first I didn't understand what you were asking. It'll shuffle through all the args you care to give it. Commented Apr 9, 2014 at 2:14
  • thanks for the script in shell itself. I will take a look into it as soon as I get into server tomorrow. :) Commented Apr 9, 2014 at 2:53
1

I found out the way to print the elements in 2 element sized combinations. The php code is as below. 

<?php
function pc_array_power_set($array) {
    // initialize by adding the empty set
    $results = array(array( ));

    foreach ($array as $element)
        foreach ($results as $combination)
            array_push($results, array_merge(array($element), $combination));
    return $results;
}
$set = array('12345', '56789', '98765');
$power_set = pc_array_power_set($set);
foreach (pc_array_power_set($set) as $combination) {
    if (2 == count($combination)) {
        print join("\t", $combination) . "\n";
    }
}
?>

The above code prints the output as,

56789   12345
98765   12345
98765   56789

Reference for the above code is here.

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1
  • if you are going to use php you might as well use python: python -c 'from itertools import combinations;from sys import stdin; print list(combinations(stdin.readline().split(), 2))' <<<'12345 56789 98765' Commented Apr 8, 2014 at 23:17

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