Generate a random filename in unix shell

Question

I would like to generate a random filename in unix shell (say tcshell). The filename should consist of random 32 hex letters, e.g.:

c7fdfc8f409c548a10a0a89a7         


        

Answer 1

Another thing you can add is running the date command as follows:

date +%S%N

Reads nonosecond time and the result adds a lot of randomness.

Answer 2

Tested in zsh, should work with any BASH compatible shell!

#!/bin/zsh

SUM=`md5sum <<EOF
$RANDOM
EOF`

FN=`echo $SUM | awk '// { print $1 }'`

echo "Your new filename: $FN"

Example:

$ zsh ranhash.sh
Your new filename: 2485938240bf200c26bb356bbbb0fa32
$ zsh ranhash.sh
Your new filename: ad25cb21bea35eba879bf3fc12581cc9

Answer 3

Grab 16 bytes from /dev/random, convert them to hex, take the first line, remove the address, remove the spaces.

head /dev/random -c16 | od -tx1 -w16 | head -n1 | cut -d' ' -f2- | tr -d ' '

Assuming that "without resorting to a program" means "using only programs that are readily available", of course.

Answer 4

Hope to add a (maybe) better solution to this topic.

Notice: this only works with bash4 and some implement of mktemp(for example, the GNU one)

Try this

fn=$(mktemp -u -t 'XXXXXX')
echo ${fn/\/tmp\//}

This one is twice as faster as head /dev/urandom | tr -cd 'a-f0-9' | head -c 32, and eight times as faster as cat /dev/urandom | tr -cd 'a-f0-9' | head -c 32.

Benchmark:

With mktemp:

#!/bin/bash
# a.sh
for (( i = 0; i < 1000; i++ ))
do
    fn=$(mktemp -u -t 'XXXXXX')
    echo ${fn/\/tmp\//} > /dev/null
done

time ./a.sh 
./a.sh  0.36s user 1.97s system 99% cpu 2.333 total

And the other:

#!/bin/bash
# b.sh
for (( i = 0; i < 1000; i++ ))
do
    cat /dev/urandom | tr -dc 'a-zA-Z0-9' | head -c 32 > /dev/null
done

time ./b.sh 
./b.sh  0.52s user 20.61s system 113% cpu 18.653 total

Answer 5

If you are on Linux, then Python will come pre-installed. So you can go for something similar to the below:

python -c "import uuid; print str(uuid.uuid1())"

If you don't like the dashes, then use replace function as shown below

python -c "import uuid; print str(uuid.uuid1()).replace('-','')"

Answer 6

The first answer is good but why fork cat if not required.

tr -dc 'a-f0-9' < /dev/urandom | head -c32