awk - function to return permutations of n items out of m


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# 8  
Code:
echo {a..e}{a..e}{a..e} | xargs -n1

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# 9  
Quote:
Originally Posted by nezabudka
Code:
echo {a..e}{a..e}{a..e} | xargs -n1

nice idea, nezabudka.
Code:
echo {a..e}{a..e}{a..e} | xargs -n1| sed 's/./& /g'

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# 10  
A very un-awk-like and more Perl-like script. Smilie

I added the sort routine because array iteration doesn't return the elements in order.
(Definitely not a good idea for large arrays.)

Note that the OP wants the results in an array for further processing in the same script.
I'm not sure how to retrieve the array elements in the order that they were inserted.
Maybe a forum member can suggest how to do so.

Code:
echo |
awk 'function generate_permutations(cs, item, n, k){
         if (k == 0){
             iter = iter + 1;
             arr[iter] = item;
             return;
         }
         for (i in cs){
             new_item = item""cs[i];
             generate_permutations(cs, new_item, n, k-1);
         }
     }
     {
          split("", arr, "");
          iter = 0;
          str = "a,b,c,d,e";
          n = split(str, charset, ",");
          k = 3;
          generate_permutations(charset, "", n, k);
          asort(arr);
          for (i=1; i <= iter; i++){
              printf "%s\n", arr[i];
          }
     }
    '


Last edited by durden_tyler; 01-09-2019 at 03:39 PM.. Reason: Too many blank lines added automatically between paragraphs.
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# 11  
Quote:
Originally Posted by nezabudka
Code:
echo {a..e}{a..e}{a..e} | xargs -n1

SUPERB!

(Just one note for viewers though, this is NOT POSIX compliant...)

EDIT:
Modified to give spaces...

Code:
Last login: Wed Jan  9 19:12:39 on ttys000
AMIGA:amiga~> text=$( echo {a..e}_{a..e}_{a..e} | xargs -n1 ); echo "${text//_/ }"
a a a
a a b
a a c
a a d
. . .
e e e
AMIGA:amiga~> _


Last edited by wisecracker; 01-09-2019 at 04:17 PM.. Reason: No choice it will add to the bottom...
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# 12  
Quote:
Originally Posted by nezabudka
Code:
echo {a..e}{a..e}{a..e} | xargs -n1

Very good idea indeed. You won't need any externals doing it like this:

Code:
for p in {a..e}{a..e}{a..e} ; do
     echo "$x"
done

This works in bash as well as ksh93 but not in ksh88 and not in Bourne shell either.

bakunin
This User Gave Thanks to bakunin For This Post:
# 13  
Thank you all for an evaluation
Probably there should replace the heavyweight utility "xargs" and wrap everything in a function
like so
Code:
#!/bin/bash
prt() {
        str=$(seq -s"{$1..$2}" $3)
        eval echo ${str//[0-9]}
}
prt a e $((3+1)) | fmt -1 | sed 's/./& /g'

Or insert a loop "for in" as suggested above.
In ksh93 works too

Last edited by nezabudka; 01-09-2019 at 04:54 PM..
# 14  
Quote:
Originally Posted by nezabudka
Thank you all for an evaluation
Probably there should replace the heavyweight utility "xargs" and wrap everything in a function
like so
Code:
#!/bin/bash
prt() {
        str=$(seq -s"{$1..$2}" $3)
        eval echo ${str//[0-9]}
}
prt a e $((3+1)) | fmt -1 | sed 's/./& /g'

Or insert a loop "for in" as suggested above.
In ksh93 works too
Too many pipes and transient commands, (utilities)...
However $((3+1)) should be $((2+1)) or $((3)) on OSX 10.14.1, default bash terminal...
Code:
Last login: Wed Jan  9 19:58:11 on ttys000
AMIGA:amiga~> cd Desktop/Code/Shell
AMIGA:amiga~/Desktop/Code/Shell> bash --version
GNU bash, version 3.2.57(1)-release (x86_64-apple-darwin18)
Copyright (C) 2007 Free Software Foundation, Inc.
AMIGA:amiga~/Desktop/Code/Shell> ./abcde.sh
a a a 
a a b 
a a c 
a a d 
a a e 
a b a 
a b b 
a b c 
. . .
e d d 
e d e 
e e a 
e e b 
e e c 
e e d 
e e e 
AMIGA:amiga~/Desktop/Code/Shell> _

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