[AMG]: unsort is a simple UNIXy stdin->stdout pipeline tool for randomizing line order.  It's simple, works quite nicely, and is surprisingly useful.

Without further ado, I present to you the source:

 #!/bin/sh
 # \
 exec tclsh "$0" "$@"

 proc main {} {
     set lines [lrange [split [read stdin] \n] 0 end-1]
     set count [llength $lines]

     for {set idx_1 0} {$idx_1 < $count} {incr idx_1} {
         set idx_2 [expr {int($count * rand())}]
         set temp [lindex $lines $idx_1]
         lset lines $idx_1 [lindex $lines $idx_2]
         lset lines $idx_2 $temp
     }

     puts [join $lines \n]
 }

 main

 # vim: set ts=4 sts=4 sw=4 tw=80 et ft=tcl:

Even though the above really is good enough, I'm still interested in seeing performance improvements.  Any ideas?

Just in case you're into ancient history, here's the slow, old, real-sorting version of main I wrote a few hours before the shiny new swappy version:

 proc main {} {
     set lines [list]
     foreach line [lrange [split [read stdin] \n] 0 end-1] {
          lappend lines [list [expr {rand()}] $line]
     }

     foreach line [lsort -real -index 0 $lines] {
         puts [lindex $line 1]
     }
 }

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Let's give it a try, shall we?

 [andy@blender|~/devel/misc]$ unsort <<EOF
 > alpha
 > bravo
 > charlie
 > delta
 > EOF
 charlie
 bravo
 delta
 alpha

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I usually use unsort for creating a randomized playlist:

 [andy@blender|~]$ mplayer $(find ~/media/music -type f | unsort)

Works great!  I'm using it right now, as a matter of fact.

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See also [Shuffling a list]

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Under which category or categories should this page be filed?

Ideas: [[
[[Category Sorting]] |
[[Category UNIX]] |
[[Category Command Line Tools]] |
[[Category Text Processing]] |
[[Category Entropy Source]] :^)
]]