How do I select a random file from a directory?

Question

I have a directory full of random files. Some of them are pictures and end with .png extension. I want to create a bash script that deletes a random .png image every time I run it. How do I do this? Please explain your answer (or put appropriate links) since I'm a complete beginner.

I tried something using the shuf command but couldn't get it to work — IgnisDa, Apr 18 '20 at 13:57
Something like `ls *.png | shuf -n 1 | xargs rm -v --`? Not really a good solution though — oguz ismail, Apr 18 '20 at 14:00
I'll just have to type that out in a terminal because I have no idea what xargs or even the '|'s mean — IgnisDa, Apr 18 '20 at 14:13

FangQ · Accepted Answer · 2020-04-18T14:19:54.520

2

use the shuf command to create a random shuffle and head -1 to pick the top one

ls -1 *.png |  shuf | head -1

or

ls -1 *.png | shuf -n 1

edited Apr 18 '20 at 14:19

answered Apr 18 '20 at 13:59

FangQ

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what does the -1 in ls and shuf do? – IgnisDa Apr 18 '20 at 14:14
`ls -1` list one file per line; `shuf -n 1` output 1 shuffled line – FangQ Apr 18 '20 at 14:16
I tried the second one, and it gave me shuf: invalid line count: ‘-1’. I replaced the last - 1 with 1 and it worked. – IgnisDa Apr 18 '20 at 14:19
Thank you very much, you were a great help! – IgnisDa Apr 18 '20 at 14:29

score 0 · Answer 2 · answered Apr 18 '20 at 18:53

Using just bash builtins to pick the file:

#!/usr/bin/env bash

shopt -s nullglob
files=(*.png)
shopt -u nullglob
if [[ ${#files[@]} -eq 0 ]]; then
  echo "No matching files!"
  exit
fi
file=${files[$((RANDOM % ${#files[@]}))]}
echo "Deleting $file"
rm -f "$file"

Adds all the matching files to an array (See How do I assign ls to an array in linux bash), and then picks a random one from it using the $RANDOM variable (Which evaluates to a new random integer each time it appears) and some math.

How do I select a random file from a directory?

2 Answers2