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create random string from /dev/urandom (or another length)

Terminal - create random string from /dev/urandom (or another length)
echo `cat /dev/urandom |tr -dc "[:alnum:]" | head -c64`
2010-12-06 20:01:56
Functions: echo head tr
create random string from /dev/urandom (or another length)


There are 2 alternatives - vote for the best!

Terminal - Alternatives
echo `cat /dev/urandom | base64 | tr -dc "[:alnum:]" | head -c64`
2010-12-06 21:04:57
User: Dereckson
Functions: echo head tr

The same command, but with a base64 filter, more forgiving for special characters than tr.

Know a better way?

If you can do better, submit your command here.

What others think

On FreeBSD 8.1:

tr: Illegal byte sequence

Comment by Dereckson 281 weeks and 4 days ago

That cat's not necessary:

echo $(</dev/urandom tr -dc "[:alnum:]" | head -c64)
Comment by eightmillion 281 weeks and 4 days ago

Your variant works only with sh, zsh and bash eightmillion.

In tcsh, you'll got "Illegal variable name." as output

By the way, head -c doesn't work on OpenBSD.

Comment by Dereckson 281 weeks and 4 days ago

It works on ash, dash, bash, sh, ksh, zsh, and sash. The only reason it doesn't work on csh variants is because they aren't posix compliant with respect to command substitution. Try:

echo `</dev/urandom tr -dc "[:alnum:]" | head -c64`
Comment by eightmillion 281 weeks and 4 days ago

Thanks for all your comments. This is my "greeting" command. Maybe another version will be later. I test and use it in my gentoo linux box with bash.

I agree that echo not needed. Its just cosmetics.

Comment by unixmonkey14859 281 weeks and 1 day ago

Your point of view

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