There are several scenarios where a cryptographic-quality random number generator might be needed within the context of a shell script. My favorite tool for th

There are several scenarios where a cryptographic-quality random number generator might be needed within the context of a shell script. My favorite tool for this is "openssl rand" and I can find the manual page on rhel7 with "man rand." Here are 8 bytes of randomness in base64: $ openssl rand -base64 8 mGHxYcVOmA8= If you like decimal: $ printf %d\\n 0x$(openssl rand -hex 2) 21924 When I've got dozens of users to create, this is how I am assigning their initial passwords. The shell's $RANDOM is somewhat less trustworthy than other sources here. It also does not appear to be POSIX, but comes from ksh88, where it is described as returning a random integer between 0 and 32767 each time it is referenced. If unset in a script, it cannot be used again for the life of the shell.