Learn Fzf - Environment Variables & Default Options

#Introduction

In episode 7 you glimpsed variables like FZF_CTRL_T_COMMAND and FZF_CTRL_R_OPTS. Episode 8 ties it all together: fzf reads its settings from environment variables built systematically, and understanding this pattern is the key to managing fzf without mixing things up. It all starts with a simple export line like export FZF_DEFAULT_OPTS="--height=40%".

Think of every fzf invocation as an airplane. The FZF_DEFAULT_OPTS variable is the global cabin setting (every plane is the same), while the per-keybinding variables are settings specific to one route. If you guess without understanding this hierarchy, the result is configuration conflicts that are hard to trace.

#Concept: One Source, Many Adjustments

All fzf configuration flows through environment variables in two families:

There are also FZF_COMPLETION_* (for fuzzy completion, episode 9) and FZF_TMUX_* (for tmux integration, its own episode). The naming pattern is always the same: FZF_<CONTEXT>_<ROLE> where COMMAND defines the data source and OPTS defines the command-line options.

#FZF_DEFAULT_COMMAND: Global Data Source

When fzf's input is not piped (for example, you type fzf directly), fzf needs a data source. The default is simple directory walking, but you can replace it with any command:

export FZF_DEFAULT_COMMAND="find . -type f -not -path '*/.git/*'"

It's important to understand: FZF_DEFAULT_COMMAND applies when fzf runs without stdin. For keybindings like CTRL-T, the data source comes from each keybinding's own dedicated variable (not directly from this one) — details in the section below. Use this variable for any file list you open often, for example combining several project directories:

export FZF_DEFAULT_COMMAND="find ~/code ~/docs -type f 2>/dev/null"

#FZF_DEFAULT_OPTS: Global Cabin Settings

This is the most important variable. Every option you've learned since episode 4 — --height, --layout, --border, --color, --preview, --bind — can be collected here so every fzf invocation is consistent:

export FZF_DEFAULT_OPTS="--height=40% --layout=reverse --border --info=inline \
  --preview='bat --color=always --style=numbers --line-range=:200 {}' \
  --color=prompt:#50fa7b,pointer:#ff79c6,hl:#bd93f9"

There is one more that's often missed: FZF_DEFAULT_OPTS_FILE. If your settings are very long, move the contents of FZF_DEFAULT_OPTS into a file and point this variable at it:

export FZF_DEFAULT_OPTS_FILE="$HOME/.config/fzf/opts"

The benefits: options are no longer bound by shell quote escaping, they can have comments, and they're easier to version-control. fzf still reads FZF_DEFAULT_OPTS and FZF_DEFAULT_OPTS_FILE at the same time — both are merged.

#Per-Keybinding Variables

Each keybinding from episode 7 has a COMMAND and OPTS variable pair. They set the data source and options for a specific fzf invocation, and override or add on top of FZF_DEFAULT_OPTS:

Note: there is no FZF_CTRL_R_COMMAND — CTRL-R's source is always the shell history; it cannot be changed. This is consistent with how episode 7 works.

Here's a typical combination: CTRL-R uses the history scheme, while CTRL-T uses preview and multi-select:

export FZF_CTRL_R_OPTS="--scheme=history --sort"
export FZF_CTRL_T_OPTS="--preview='bat --color=always {}' --multi"

Because OPTS is added to FZF_DEFAULT_OPTS, you don't need to repeat global options in every variable — just add the specific ones. If a per-keybinding OPTS contains the same option as the global one, the value from that OPTS wins.

#Best Configuration Patterns

The best fzf setup is one another person can read in a minute. The recommendation: a tidy block of sections at the end of your config, ordered from global to specific.

# ---------- Fzf: global data source ----------
export FZF_DEFAULT_COMMAND="find . -type f -not -path '*/.git/*'"
 
# ---------- Fzf: global options ----------
export FZF_DEFAULT_OPTS="--height=40% --layout=reverse --border \
  --info=inline --prompt='> ' \
  --preview='bat --color=always --style=numbers --line-range=:200 {}' \
  --color=prompt:#50fa7b,pointer:#ff79c6,hl:#bd93f9"
 
# ---------- Fzf: per keybinding options ----------
export FZF_CTRL_T_OPTS="--preview='ls -la' --multi"
export FZF_CTRL_R_OPTS="--scheme=history --sort"
export FZF_ALT_C_OPTS="--preview='ls -la'"
 
# ---------- Fzf: load shell integration ----------
eval "$(fzf --bash)"

One management key: because CTRL-R only has OPTS (no COMMAND), and its data source is already fixed, don't waste time looking for a variable that doesn't exist. The FZF_<CONTEXT>_<ROLE> naming pattern immediately tells you what can be changed.

#Closing

Episode 8 made your fzf configuration centralized and systematic: FZF_DEFAULT_COMMAND for the global data source, FZF_DEFAULT_OPTS for global settings, per-keybinding variables (FZF_CTRL_T_*, FZF_CTRL_R_OPTS, FZF_ALT_C_*) for specific adjustments, FZF_DEFAULT_OPTS_FILE for long options, and a tidy config block pattern.

The key takeaways:

• FZF_DEFAULT_* applies globally; per-keybinding variables add on top of it.
• COMMAND sets the data source; OPTS sets options; CTRL-R only has OPTS.
• Quote options that contain spaces inside the variable value.
• Order your config: global → per-bind → shell integration.

In episode 9, we will cover fuzzy completion (**<TAB>) — how fzf completes commands, paths, processes, and even environment variables, plus building your own custom completer. See you in episode 9!