Fuzzy Filter

fuzzy-filter — Non-Interactive Fuzzy Search Pipelines

Overview

fzf is famous as an interactive picker, but it also has a batch mode: fzf --filter QUERY reads lines on STDIN, fuzzy-ranks them against QUERY, prints the matches to STDOUT, and exits — no terminal UI, no keyboard, fully scriptable. Pair it with a fast scanner and you get a two-stage pipeline:

                regex / literal scan            fuzzy rank
  files/dirs ──────────────────────▶ lines ──────────────────▶ ranked matches
                rg · fd · rga                  fzf --filter QUERY

1. Stage 1 — scan (regex): rg, fd, or rga walks the tree and emits candidate lines (file paths, file:line:content rows, or document text). This stage is gitignore-aware and uses regular expressions.
2. Stage 2 — rank (fuzzy): fzf --filter keeps only the lines that fuzzy-match QUERY and orders them best-first. This stage uses fzf's fuzzy syntax — NOT regex (see Fuzzy filter syntax).

The two query languages are different on purpose. Use a broad/empty Stage-1 pattern (. matches every line) to hand fzf the full candidate set, then let the fuzzy query do the selective work — or pre-narrow with a real regex in Stage 1 when you know it, and fuzzy-rank the remainder.

This is exactly how the fuzzy-search MCP server works internally; this skill documents the underlying commands so you can run them directly. See references/pipelines.md for the exact MCP-equivalent command behind each tool.

When to Use This Skill (and When Not To)

Use this non-interactive technique when you want fuzzy results from a script, a single command, or to pipe ranked output onward — no TUI involved.

Key distinctions:

• vs. the fzf skill: that skill covers interactive selection (previews, keybindings, CTRL-T/CTRL-R, live-grep frontends). Here fzf never draws a UI — --filter makes it a Unix filter.
• vs. the fuzzy-search MCP: the MCP exposes these pipelines as model tools with typed arguments and parsed results. Reach for it when you want tool-call ergonomics; reach for this skill when you're already in a shell.
• vs. rg/fd alone: if a regex answers the question, you don't need fzf. Add fzf --filter only when you specifically want fuzzy (typo-tolerant, subsequence) ranking.

Prerequisites

rg --version      # ripgrep — Stage-1 scanner for files & content
fzf --version     # fzf     — Stage-2 fuzzy ranker (needs batch --filter)

Required for everything: rg and fzf. Optional, per use case:

• fd — ergonomic file-list source for fuzzy file search (alternative to rg --files).
• rga (ripgrep-all) — for document/PDF content (PDFs, Office docs, ebooks, archives, sqlite). (rga 0.10+)
• pdftotext (poppler) or PyMuPDF — to extract/inspect PDF pages once you've located a hit. See references/pdf.md.

If a required binary is missing, stop and tell the user — do not auto-install. See the ripgrep, fd, and fzf skills for installation instructions.

Fuzzy Filter Syntax

Stage 2 uses fzf's extended-search syntax, the same language as the interactive prompt. A bare term is a fuzzy (subsequence) match; prefix/anchor sigils make terms exact. Space-separated terms are ANDed.

So def test_ seer credit means: fuzzy-def test_ AND fuzzy-seer AND fuzzy-credit, in any order. This is not a regex — ., *, (, [ are literal characters here, not metacharacters. (Same language as the fzf skill's "Search Syntax" section — batch and interactive use the same matcher.)

Space is the AND separator — backslash-escape it to match a literal space. Because a bare space splits terms, a multi-word phrase like a function signature must escape its spaces: 'def\ parse_config matches the contiguous string def parse_config, whereas 'def 'parse_config (two exact terms) matches those two substrings independently anywhere on the line. Use \ when adjacency matters. The escape survives the shell inside double quotes (fzf --filter "'def\ parse_config"), and through the fuzzy-search MCP it is just a literal backslash in the fuzzy_filter string.

Code-navigation idioms

These compose the operators above into the patterns you actually reach for when moving around a codebase (a bare-fuzzy query is rarely precise enough on its own):

The recurring shape is exact term(s) ('…, with \ for phrases) + !path exclusions — anchor on what you know literally, then subtract the noise.

Smart-case applies to the fuzzy query too: an all-lowercase query is case-insensitive; any uppercase letter makes it case-sensitive — the same rule rg/fd use. --exact also works in batch mode (fzf --exact --filter Q): bare terms become exact substring matches, and the '-prefix flips to mean "unquote" (fuzzy).

Fuzzy FILE Search

Feed fzf a list of paths and fuzzy-rank them by path.

# Source the file list with ripgrep (gitignore-aware), fuzzy-rank by path
rg --files | fzf --filter 'src model user'

# fd as the source instead (also gitignore-aware; matches names by default)
fd --type f | fzf --filter 'test util'

# Include hidden files in the candidate set
rg --files --hidden | fzf --filter 'config yaml'

Bias ranking toward path structure with fzf's path scheme — it weights matches near path separators, which is what you usually want for filenames:

rg --files | fzf --scheme=path --filter 'cmd main'   # (fzf 0.36+)

NUL-safety (paths with spaces/newlines)

A newline-delimited pipe breaks on filenames containing newlines. Make the whole pipe NUL-delimited end-to-end:

rg --files --null | fzf --read0 --print0 --filter 'src model' \
  | xargs -0 -n1 echo            # hand off safely to the next tool

fd --print0 --type f | fzf --read0 --print0 --filter 'big report' \
  | xargs -0 "$EDITOR"

--read0 makes fzf read NUL-separated input; --print0 makes it emit NUL-separated output. Always pair with xargs -0.

Fuzzy CONTENT Search

Scan every line, then fuzzy-rank the file:line:content rows. This is the workhorse pipeline.

rg --line-number --no-heading --color=never . PATH \
  | fzf --filter 'QUERY' --delimiter : --nth=1,3..

Stage 1 anatomy:

• . — match every line (hand the full set to fzf). Swap in a real regex to pre-narrow.
• --line-number — prefix each row with its line number (field 2).
• --no-heading — one self-contained file:line:content row per match (no grouped headers).
• --color=never — mandatory: ANSI color codes would corrupt fzf's matching and field splitting.

Stage 2 anatomy — the row is FILE : LINE# : CONTENT, so with --delimiter ::

• field 1 = file path, field 2 = line number, field 3.. = the line content (which may itself contain colons — 3.. captures all of it).
• --nth=1,3.. — fuzzy-match against path + content, deliberately skipping field 2 (the line number) so digits in your query don't spuriously match line numbers.

Content-only (ignore the path)

To match only the code/text and never the file path:

rg --line-number --no-heading --color=never . PATH \
  | fzf --filter 'QUERY' --delimiter : --nth=3..

--nth=3.. restricts fuzzy matching to field 3 onward (content), ignoring both the path (field 1) and the line number (field 2). Use this when a path component keeps polluting your results.

The full output row (including file:line:) is still printed — --nth only controls what fzf matches on, not what it emits. That's what lets you pipe the result into an editor at the right line. To emit only chosen fields, use --accept-nth (fzf 0.60+) — e.g. --accept-nth='{1}:{2}' prints file:line ready for code --goto.

Field Scoping Deep-Dive

--nth is the lever that makes content search precise. It selects which delimiter-separated fields fzf searches; --with-nth selects which fields it displays.

Field ranges: N (one field), N.. (N to end), ..N, N..M, and comma-joined lists like 1,3... Negative indices count from the end (-1 = last field). Default delimiter is AWK-style runs of whitespace; set --delimiter explicitly whenever fields are colon- or tab-separated.

Why skip field 2? ripgrep puts the line number there. If you matched on it, a query like 120 would rank every line near line 120 across all files. 1,3.. / 3.. exclude it so numbers in your query match real content.

Document & PDF Fuzzy Search

rga (ripgrep-all) extends rg to PDFs, Office docs, ebooks, archives, and sqlite by transparently extracting their text. Scan with rga, then fuzzy-rank the same way. (rga 0.10+)

# Plain rows — flatten to file:line:content, then fuzzy-rank the content
rga --no-heading --line-number --color=never . PATH \
  | fzf --filter 'QUERY' --delimiter : --nth=3..

# Restrict to PDFs only (rga adapter), still fuzzy-ranked
rga --no-heading --line-number --color=never --rga-adapters=+poppler . PATH \
  | fzf --filter 'QUERY' --delimiter : --nth=3..

The fuzzy-search MCP's fuzzy_search_documents uses rga --json and parses the JSON events; on the CLI the flattened --no-heading --line-number form above is the simpler equivalent. For the JSON variant, adapter list, and PDF extraction/outline commands (the CLI analog of the MCP's PDF tools), see references/pdf.md.

Gotchas

• Fuzzy ≠ regex. The Stage-2 query is fzf syntax. ./*/[ are literals; there are no capture groups or quantifiers. Put real regexes in Stage 1 (rg/fd/rga).
• --color=never before filtering. Without it, ANSI escapes ride along inside field 3 and wreck both matching and any downstream parsing. (Interactive fzf uses --ansi to render color; in batch mode you strip it instead.)
• Skip the line-number field. Use --nth=1,3.. or --nth=3.. with --delimiter :; matching on field 2 lets stray digits match line numbers.
• NUL-safety. For paths that may contain spaces/newlines, go end-to-end NUL: rg --files --null/fd --print0 → fzf --read0 --print0 → xargs -0.
• Empty query returns everything. fzf --filter '' passes all input through (ranked as-is). Guard against an empty query in scripts if you don't want the whole tree.
• Exit code 1 = no matches, not an error. fzf --filter exits non-zero when nothing matches; handle it explicitly in set -e scripts.
• fzf still reads everything. --filter consumes all of STDIN before printing. For huge inputs, pre-narrow in Stage 1 (a real rg regex, -t/-g filters) so fzf ranks a smaller set.

See Also

• fzf skill — the interactive counterpart: live pickers, previews, --bind, CTRL-T/CTRL-R, and the full Search Syntax reference.
• ripgrep skill — Stage-1 content scanning: regex, -t/-g filters, --json, gitignore behavior.
• fd skill — Stage-1 file-list source: name/glob/metadata filtering, --print0.
• fuzzy-search MCP (mcp__plugin_fuzzy-search_fuzzy-search__*) — these same pipelines as typed model tools (content/file/document search + PDF tools).

References

• references/pipelines.md — full recipe catalog (files/content/docs, NUL-safe, limiting, sorting, xargs/clipboard/editor hand-off — best hit → pbcopy or code/cursor --goto file:line) plus the exact MCP-equivalent command for every fuzzy-search tool.
• references/pdf.md — rga configuration and PDF page extraction/outline via pdftotext/PyMuPDF (CLI analog of the MCP's PDF tools).