A configuration to maintain history across sessions and share it across terminals in ZShell

.zshrc

##############################################################################
# History Configuration
##############################################################################
HISTSIZE=5000               #How many lines of history to keep in memory
HISTFILE=~/.zsh_history     #Where to save history to disk
SAVEHIST=5000               #Number of history entries to save to disk
#HISTDUP=erase               #Erase duplicates in the history file
setopt    appendhistory     #Append history to the history file (no overwriting)
setopt    sharehistory      #Share history across terminals
setopt    incappendhistory  #Immediately append to the history file, not just when a term is killed

Hey. I use someone else's .zshrc config and there were two lines in it. The first one was #setopt SHARE_HISTORY and the second one was setopt sharehistory, like in your snippet. Do you know what the difference would be between the two?

From ZSH docs:

Options are primarily referred to by name. These names are case insensitive and underscores are ignored. For example, ‘allexport’ is equivalent to ‘A__lleXP_ort’.