First index, first search

1. Write a configuration

mkdir -p ~/.config/fast_code_search
fast_code_search_server --init ~/.config/fast_code_search/config.toml

Open the file and set paths to the directories you want searchable. The defaults for everything else are sensible; the keys worth knowing early:

[indexer]
paths = ["~/work", "~/src/another-repo"]     # ~ expands; relative paths resolve against this file
index_path = "~/.local/share/fast_code_search/index.fcsidx"   # persist the index across restarts
watch = true                                   # the default: follow edits, renames and deletes

Both binaries find this file on their own ($FCS_CONFIG, ./fast_code_search.toml, then ~/.config/fast_code_search/config.toml), so you rarely need --config. The full key list is in API and configuration.

2. Start the server

fast_code_search_server

It logs how many files it discovered and indexes them in batches; searches work while the build is still running. A first build of a 60k-file workspace takes a couple of minutes (tree-sitter symbol extraction is most of it); later starts load the saved index in seconds and reconcile what changed while the server was down.

3. Search

From another terminal:

fcs 'fn main'                 # lines holding the phrase, like rg -F -i
fcs symbols SearchEngine      # definitions only
fcs refs SearchEngine         # call sites and type mentions
fcs -e 'fn\s+\w+\(' -g '*.rs' # a regex, Rust files only
fcs status                    # is the server up, what does it hold

Or open http://127.0.0.1:8080 for the web UI, or call the API:

curl "http://127.0.0.1:8080/api/search?q=fn%20main&max=5"

4. Keep it running

The server is meant to stay up: the index lives in memory and the watcher keeps it current. Run at startup shows the per-user service on Linux, macOS and Windows.