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

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