Random Numbers in Bash

Re:Random Numbers in Bash by chasil on Monday March 27, 2023 @11:54AM (#35328273)

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=

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.

[ Parent | on HN ]

Re:Random Numbers in Bash by TRiG_Ireland on Monday March 27, 2023 @12:46PM (#35328962)

I use this to create passwords when I need to manually:

    function password_generate { head -c ${1-12} /dev/urandom | base64; }

[ Parent | on HN ]

Re:Random Numbers in Bash by chasil on Monday March 27, 2023 @01:27PM (#35329565)

Sometimes, extreme portability makes us do desperate things.

  # uname -a
  HP-UX prdcrm B.10.20 A 9000/800 862741461 two-user license

  # ls -l /dev/urandom
  /dev/urandom not found

  # openssl rand -base64 8
  v51U1RvSD2Q=

I could run this on VAX VMS if you want.

[ Parent | on HN ]