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Full Discussion: awk - function to return permutations of n items out of m
Top Forums Shell Programming and Scripting awk - function to return permutations of n items out of m Post 303028487 by cjnwl on Wednesday 9th of January 2019 11:15:45 AM
Old 01-09-2019
awk - function to return permutations of n items out of m
Hi,

I'm trying to write an awk function that returns all possible permutations of n items chosen in a list of m items. For example, given the input "a,b,c,d,e" and 3, the function should return the following :
Code:
a a a
a a b
a a c
a b a
a b b
...
c a a
c a b
...
e e c
e e d
e e e

(125 lines = 5 ^^ 3).

I've managed to write a function with nested loops that works, but only for a predetermined depth. I can't seem to manage the recursion if I want n to be variable.

Also, an added difficulty is that I need the results in an array for further processing in the same script, not just output to the console.

Any help would be much appreciated.
Chris
 

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LEARN ABOUT DEBIAN

cvtbatch

CVTBATCH(8)						      System Manager's Manual						       CVTBATCH(8)

NAME

       cvtbatch - convert Usenet batch file to INN format

SYNOPSIS

       cvtbatch [ -w items ]

DESCRIPTION

       Cvtbatch  reads	standard  input  as a series of lines, converts each line, and writes it to standard output.  It is used to convert simple
       batchfiles that contain just the article name to INN batchfiles that contain additional information about each article.

       Each line is taken as the pathname to a Usenet article.	If it is not an absolute pathname, it is taken relative to  the  spool	directory,
       /var/spool/news.  (Only the first word of each line is parsed; anything following whitespace is ignored.)

OPTIONS

       -w     The  ``-w''  flag  specifies  how  each output line should be written.  The items for this flag should be chosen from the ``W'' flag
	      items as specified in newsfeeds(5).  They may be chosen from the following set:
		   b	Size of article in bytes
		   f	full pathname of article
		   m	article message-id
		   n	relative pathname of article

       If the input file consists of a series of Message-ID's, then use grephistory(1) with the ``-s'' flag piped into cvtbatch.

HISTORY

       Written by Rich $alz <rsalz@uunet.uu.net> for InterNetNews.  This is revision 1.4, dated 1996/10/29.

SEE ALSO

       grephistory(1) newsfeeds(5).

																       CVTBATCH(8)
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