[SOLVED] Randomly select a folder using Shell Scripting

kapz_unlocked · 06-17-2011, 02:08 AM

Hi,
There are five folders in a folder and I want to select one randomly.
I used this command:

Code:

rand1="${loc[RANDOM % ${#loc[@]}]}"

but it selects files too. I have no idea about this code even. I found it on a forum.
Can anybody help me to select only a directory, not files?
Thanks in advance!

colucix · 06-17-2011, 02:17 AM

RANDOM is a built-in variable that returns an integer between 0 and 32767 every time it is referenced. If you have the names of the folders in the array loc, the expression

Code:

$RANDOM % ${#loc[@]}

gives the remainder of the division between a random integer and 5, that is a number between 0 and 4. This is used as index to select an element of the array. What do you mean by "it selects files too"? There is no reference to files here, only a reference to the content of the array loc. If it contains only the names of the directories, you will select one of them randomly.

kapz_unlocked · 06-17-2011, 02:28 AM

Quote:

Originally Posted by colucix

RANDOM is a built-in variable that returns an integer between 0 and 32767 every time it is referenced. If you have the names of the folders in the array loc, the expression

Code:

$RANDOM % ${#loc[@]}

gives the remainder of the division between a random integer and 5, that is a number between 0 and 4. This is used as index to select an element of the array. What do you mean by "it selects files too"? There is no reference to files here, only a reference to the content of the array loc. If it contains only the names of the directories, you will select one of them randomly.

Sorry but 'loc' here is not an array. The code comes like:

Code:

loc=(/root/shared_storage/*)
rand1="${loc[RANDOM % ${#loc[@]}]}"

This gives me paths of different files/ folders in '/root/shared_storage/' folder. what I need to do is to avoid getting a file path to rand1. I need only a directory.

ssrameez · 06-17-2011, 02:36 AM

I am not much familiar with this command.. But wrote a script for you. See if it useful for you.

Quote:

#!/usr/bin/perl

use strict;
use warnings;

my $dir = $ENV{'PWD'};
opendir(DIR,"$dir") or die "Unable to open dir $dir:$!\n";

my @dirs = grep {!/^\./ && -d "$dir/$_" } readdir(DIR);

my $range = $#dirs;

my $random_number = int(rand($range));

print "Random number $random_number\n";
print "My Random Directory is $dirs[$random_number]\n";

Verified
========

Quote:

./rand_dir.pl
Random number 0
My Random Directory is test1

./rand_dir.pl
Random number 2
My Random Directory is test3

Reuti · 06-17-2011, 02:45 AM

Quote:

Originally Posted by kapz_unlocked

Code:

loc=(/root/shared_storage/*)
rand1="${loc[RANDOM % ${#loc[@]}]}"

Maybe you can use find:

Code:

loc=($(find . -maxdepth 1 -type d))

kapz_unlocked · 06-17-2011, 02:54 AM

Thanks ssrameez! But I don't know to embed perl with my script.

Anyway

Code:

if [ -f $rand1 ]; then
			rand1="${loc[RANDOM % ${#loc[@]}]}"

within a loop solved the problem!!

Thanks again you two who tried to help!

colucix · 06-17-2011, 03:34 AM

Quote:

Originally Posted by kapz_unlocked

Sorry but 'loc' here is not an array. The code comes like:

Code:

loc=(/root/shared_storage/*)
rand1="${loc[RANDOM % ${#loc[@]}]}"

This gives me paths of different files/ folders in '/root/shared_storage/' folder. what I need to do is to avoid getting a file path to rand1. I need only a directory.

Actually loc is an array, since

Code:

loc=( something )

is the syntax to assign arrays in bash. To retrieve only directories using a wildcard, put a trailing slash:

Code:

loc=(/root/shared_storage/*/)
rand1="${loc[RANDOM % ${#loc[@]}]}"

kapz_unlocked · 06-21-2011, 12:02 AM

Thank you colucix. Didn't know the facts you mentioned