Navigating through one those awesome pages on Github, I found this command to generate passwords on linux/bsd/osx:
$ LC_ALL=C tr -d -c "[:alpha:][:alnum:]" < /dev/urandom | head -c 20 c1L5CT6L0knxdVmXVWZa
Pretty nice, uh? You ran it, it generates a string with 20 characters of number and letters. Yes. But how??? tr is one of those simple commands that sometimes you took time to understand what it does.
I decided that I would understand what it does. It took sometime but I (almost) managed it:
LC_ALL=C => set tr to use C locale. ( I’ll have to write a post about locale.)
tr => command to translate or remove characters.
-d => delete the following chars
-c”[:alpha:][:alnum:]”=> Everything but this chars. So, joined with -d, tr will NOT remove letters and numers
< /dev/urandom => generate random numbers and chars and send to tr. However it generate a lot of special characters which are remove by the switches just described.
|head -c 20 => receive tr output until it reaches 20 chars and prints it.
If you wan to generate a password with special characters you can use this:
$LC_ALL=C tr -d -c "[:print:]" < /dev/urandom | head -c 20
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