Generate a random filename in unix shell

unix shell random tcsh
R S picture R S · May 8, 2010 · Viewed 55.8k times · Source

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

c7fdfc8f409c548a10a0a89a791417c5

(to which I will add whatever is neccesary). The point is being able to do it only in shell without resorting to a program.

Answer

fmark picture fmark · May 8, 2010

Assuming you are on a linux, the following should work:

cat /dev/urandom | tr -cd 'a-f0-9' | head -c 32

This is only pseudo-random if your system runs low on entropy, but is (on linux) guaranteed to terminate. If you require genuinely random data, cat /dev/random instead of /dev/urandom. This change will make your code block until enough entropy is available to produce truly random output, so it might slow down your code. For most uses, the output of /dev/urandom is sufficiently random.

If you on OS X or another BSD, you need to modify it to the following:

cat /dev/urandom | env LC_CTYPE=C tr -cd 'a-f0-9' | head -c 32

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