1. sha256sum

date +%s | sha256sum | base64 | head -c 32  ; echo

2. /dev/urandom

<  /dev/urandom tr -dc _A-Z-a-z-0-9  | head -c${1:-32};echo;
#或
tr -cd '[:alnum:]'  <  /dev/urandom | fold -w30 | head -n1
#或
<  /dev/urandom tr -dc _A-Z-a-z-0-9  | head -c6
#或
</dev/urandom tr -dc '12345!@#$%qwertQWERTasdfgASDFGzxcvbZXCVB'  | head -c8; echo ""

3. openssl

openssl rand -base64 32

4. dd

dd if=/dev/urandom bs=1 count=32  2>/dev/null | base64 -w 0  | rev | cut -b 2-  | rev

5. string

strings /dev/urandom | grep -o '[[:alnum:]]'  | head -n 30  | tr -d 'n'; echo

6. date+md5sum

date | md5sum