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Pick random file from ls command.

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# 1  
Old 02-04-2010
Pick random file from ls command.
Lets say I want to pick a random file when I do an "ls" command. I don't have set number of files in each directory.

Code:
ls | head -1

This gives me the first one in each directory, is there a way to do the same but pick a random one.
# 2  
Old 02-04-2010
A bit odd, but...
Code:
ls | sed $((RANDOM%$(ls | wc -w)+1))!d\;q

or
Code:
ls | head -$((RANDOM%$(ls | wc -w)+1)) | tail -1

# 3  
Old 02-04-2010
First one didn't work
ls | sed $((RANDOM%$(ls | wc -w)+1))!d
-bash: !d: event not found

The second one works perfectly. Can you help me understand how it works? thanks.
# 4  
Old 02-04-2010
Hey, you're right!

Works in KSH (on AIX) but not in Bash.

Code:
ls | sed -n "$((RANDOM%$(ls | wc -l)+1))p"

(changed wc to use -l)

Quote:
Originally Posted by elbombillo
Can you help me understand how it works? thanks.
  • do an ls, and pipe to output to sed
  • get a random number with modulo of the number of files (i.e. pick a number between 1 and the number of files in the directory). $RANDOM is a special variable that returns a "random" number between 0 and 32K-1
  • tell sed not to print anything except that line number (i.e. that file)
Last edited by Scott; 02-04-2010 at 02:46 PM..
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