ksh_history_rc

# Some history manipulations for Korn shells. Potential side effects unknown.
# The idea is that I don't want to commit to having a separate history file
# for EVERY interactive shell or deal with merging per-instance histories back
# into the main history, but sometimes it's nice to have a different history
# in the current shell instance (tty, xterm, whatever)

# history+      Increment the command history file version
# history-      Decrement the command history file version
# historyoff    Enter subshell with no command history
# historyon     Cancel historyoff (exit subshell)

# Relies on a default HISTFILE variable being set.
# Enable by putting a non-empty string in the initial test.
if [ -n "history" ] && [ -n "$HISTFILE" ]; then
  export THISSHELL="$0"
  if [ -z "$BASEHISTFILE" ]; then
    export BASEHISTFILE=$HISTFILE
  fi
  if [ -z "$HISTFILENUM" ]; then
    export HISTFILENUM=0
  elif [ $HISTFILENUM -gt 0 ]; then
    export HISTFILE=$BASEHISTFILE.$HISTFILENUM
  elif [ $HISTFILENUM -lt 0 ]; then
    export HISTFILE=/dev/null
  fi
  history+ () {
    if [ $HISTFILENUM -lt 0 ]; then
      echo command history disabled. Not updating HISTFILE
    else
      export HISTFILENUM=$(($HISTFILENUM + 1))
      export HISTFILE=$BASEHISTFILE.$HISTFILENUM
      echo Using command history in $HISTFILE
    fi
  }
  history- () {
    if [ $HISTFILENUM -lt 0 ]; then
      echo command history disabled. Not updating HISTFILE
    elif [ $HISTFILENUM -eq 0 ]; then
      echo Already using default history file. Not updating HISTFILE
    else
      export HISTFILENUM=$(($HISTFILENUM - 1))
      if [ $HISTFILENUM -eq 0 ]; then
        export HISTFILE=$BASEHISTFILE
      else
        export HISTFILE=$BASEHISTFILE.$HISTFILENUM
      fi
      echo Using command history in $HISTFILE
    fi
  }
  historyoff () {
    if [ $HISTFILENUM -ge 0 ]; then
      echo Starting new subshell without command history
      echo Type \"historyon\" or \"exit\" to resume regular command history func
tion
      echo NOTE: This does NOT disable in-memory command history
      HISTFILENUM=-1 $THISSHELL
      echo Command history resumed. HISTFILE=\"$HISTFILE\"
    fi
  }
  historyon () {
    [ $HISTFILENUM -lt 0 ] && exit
  }
fi