On korn shell, how to share history between regular user and root?

Shell Programming and Scripting
1

I'm exploring OpenBSD and want to stick to its default shell, which is ksh. My goal is for my regular user ("bruno") and root user to have a shared history file. However, it seems that when running as root, ksh refuses to write to a HISTFILE that is owned by non-root user. This illustrates the issue:

$ echo $0
  ksh
$ HISTFILE=/home/bruno/history  
$ chmod 777 /home/bruno/history
$ echo test
  test
$ cat /home/bruno/history
  chmod 777 /home/bruno/history
  echo test
  cat /home/bruno/history
$ su
 Password:
# HISTFILE=/home/bruno/history
# echo $HISTFILE
  /home/bruno/history
# echo test2
  test2
# cat /home/bruno/history
  chmod 777 /home/bruno/history
  echo test
  cat /home/bruno/history
  su

As you can see, the commands that are run as root do not appear in /home/bruno/history. Why won't root session in ksh write to the specified HISTFILE? If it is a ksh security feature, how do I turn it off?

2

Why not write a little cron script to combine the two files?

3

That's a good idea, but I wanted something more real-time, so I came up with a hack. If I put this in both ~/.kshrc and /root/.kshrc, I get what I want:

prompt_commands()
{
    if [ $(id -u) = "0" ]; then
        tail -1 /root/.ksh_history >>/home/bruno/.ksh_history
    else
        tail -1 /home/bruno/.ksh_history >>/root/.ksh_history
    fi
}

PS1='$(prompt_commands)'

Unlike bash, ksh does not have the handy PROMPT_COMMAND. However, the PS1 variable does support command substitution, which my hack exploits. As long as both user's and root's history files have write permission for "others", now whenever root runs a command that command gets appended to my regular user's history, and vice-versa.

1 Like
4

I like your solution better than my suggestion.

Thanks for posting back what you came up with!