My notes on setting up history-related features for zsh.

History settings

Some env variable controlling the behaviour of history feature:

# the detailed meaning of the below three variable can be found in `man zshparam`.
export HISTFILE=~/.histfile
export HISTSIZE=1000000   # the number of items for the internal history list
export SAVEHIST=1000000   # maximum number of items for the history file

# The meaning of these options can be found in man page of `zshoptions`.
setopt HIST_IGNORE_ALL_DUPS  # do not put duplicated command into history list
setopt HIST_SAVE_NO_DUPS  # do not save duplicated command
setopt HIST_REDUCE_BLANKS  # remove unnecessary blanks
setopt INC_APPEND_HISTORY_TIME  # append command to history file immediately after execution
setopt EXTENDED_HISTORY  # record command start time

In the above config, option EXTENDED_HISTORY makes sure that zsh record the time that a certain command is executed. By default, command typed in a shell session are saved in the internal command history list. When the shell exits, commands in the internal history list will be written to HISTFILE. Option INC_APPEND_HISTORY_TIME changes this behavior: right after you have executed some command, it will be written to the history file, along with the time spent to execute it. Refer to man zshoptions for more details.


history command shows only 16 items?

In zsh, if I use history command, only 16 items are shown, which is far less than the actual command history stored in HISTFILE. Why? According to the doc (man zshbuiltins), history command is just an alias to fc -l. The doc for fc command says:

fc -l [ -LI ] [ -nrdfEiD ] [ -t timefmt ] [ -m match ] [ old=new … ] [ first [ last ] ]

If first is not specified, it will be set to -1 (the most recent event), or to -16 if the -l flag is given. If last is not specified, it will be set to first, or to -1 if the -l flag is given.

So when we use command history, what we actually use is fc -l -16 -1, so the most recent 16 items in history are shown.

We can create an alias to change this:

# show all the history stored.
alias history="fc -l 1`


Search history command more effectively?

As programmers, we sometimes use a command with long options and parameters. Later on, when we want to run that command again or modify it a bit, it would be time-consuming to type it all over. I know that we can use Ctrl-R to search the command history. However, its features are limited.

I find fzf works better for this task, which supports fuzzy-search your command history. To install fzf, run the following command:

git clone --depth 1 ~/.fzf
# say yes to its install prompts

Restart the shell, you should get a far better experience searching your history commands (the shortcut is still Ctrl-R). To navigate the search results, use Ctrl-N and Ctrl-P.

Replace part of last command and re-execute

In Bash, we can use fc -s old=new to replace string old in the last command executed to new and execute it again. Bash built-in fc is different from zsh fc.

For fc in zsh, there is no -s option. The zsh equivalent is fc -e -. -e options can be found in man zshbuiltins.

Zsh also provides r command which is same as fc -e -. You do not need to define an alias for that any more.