🔀 Formats

fimod supports seamless conversion between multiple formats. Formats are auto-detected from file extensions, or set explicitly with --input-format / --output-format.

📋 JSON (.json)

• Input: Parsed as standard JSON.
• Output: Serialized as pretty-printed JSON.
• Structure: Can be Object {}, Array [], or any JSON value.

📃 NDJSON (.ndjson, .jsonl)

Newline-Delimited JSON — one JSON value per line. Ideal for streaming data, logs, and event records.

• Input: each non-empty line is parsed as a JSON value; result is an array of those values.
• Output: each array element is serialized as compact JSON on its own line (trailing newline). A non-array result is a single line.

# 🔍 Filter an NDJSON log
fimod s -i events.ndjson -e '[e for e in data if e["level"] == "error"]'

# 🔀 JSON array → NDJSON
fimod s -i users.json -e 'data' --output-format ndjson

# 🔗 Slurp + NDJSON
cat *.json | fimod s --slurp -e 'data' --output-format ndjson

📝 YAML (.yaml, .yml)

• Input: Parsed into JSON-compatible structure. Anchors and custom types are normalized.
• Output: Serialized as YAML.

⚙️ TOML (.toml)

• Input: Parsed into JSON-compatible structure.
• Output: Serialized as TOML.

📊 CSV (.csv, .tsv)

• Input: Parsed as an array of objects. Each row becomes a dict where keys are column headers.
• Output: Serialized from an array of objects. Keys of the first object become headers.

CSV options

headers global

When the input has a header row, a headers global (list of column names in file order) is injected automatically. Not available with --csv-no-input-header.

Mold defaults can also set CSV options — see Mold Defaults.

📄 TXT (.txt, .text)

• Input: data is a raw string — the entire file content, as-is.
• Output: String values are written raw. Non-string values are serialized as compact JSON.

# 🔤 data is a string
fimod s -i notes.txt -e 'data.strip().upper()'

# 📦 Return non-string → compact JSON
fimod s -i notes.txt -e '{"length": len(data)}'

📑 Lines (--input-format lines)

Splits input into an array of strings, one per line. Never auto-detected — use --input-format lines explicitly.

• Input: ["line1", "line2", ...]. Handles \n and \r\n. Trailing newline does not produce an empty element.
• Output: each element on its own line. Objects/dicts serialized as compact JSON (NDJSON).

# 🔤 Uppercase each line
fimod s -i data.txt --input-format lines -e '[l.upper() for l in data]'

# 🔍 Filter lines
fimod s -i app.log --input-format lines -e '[l for l in data if "ERROR" in l]'

# 📦 JSON array → one item per line
fimod s -i names.json -e 'data' --output-format lines

📥 Raw (--output-format raw)

An output-only format for downloading binary streams or raw bytes. Bypasses the normal data serialization pipeline completely.

• Input: Not supported.
• Output: The raw byte stream (e.g. from an HTTP response payload). Requires --input-format http.

🔥 HTTP (--input-format http)

By default, -i https://... fetches the URL and parses the body directly (format auto-detected from Content-Type). Use --input-format http when you need more than the body: status codes, response headers, redirects, or conditional logic on the response.

data is then a dict with the full response envelope:

data = {
    "status": 200,
    "headers": {"content-type": "application/json", ...},
    "body": "..."  # raw string
}

# Inspect redirect target
fimod s -i https://github.com/pytgaen/fimod/releases/latest \
    --input-format http --no-follow \
    -e 'data["status"]' --output-format txt
# → 302

# With --input-format http, data["body"] is a raw string — re-parse it explicitly
fimod s -i https://jsonplaceholder.typicode.com/users \
    --input-format http \
    -e 'set_input_format("json"); data["body"]' \
    -e 'len(data)'

🎯 Output format resolution

When --output-format is not specified, fimod resolves the output format automatically using this cascade:

# JSON in → JSON out (no flag needed)
fimod s -i data.json -e '[x for x in data if x["active"]]'

# CSV in → CSV out (no flag needed)
fimod s -i users.csv -e '[r for r in data if r["role"] == "admin"]'

# Lines in → lines out (no flag needed)
env | fimod s --input-format lines -e '[l for l in data if "PATH" in l]'

🔀 Format conversion

Convert between formats using a pass-through expression and either an output file extension or --output-format:

fimod s -i config.yaml -e 'data' -o config.toml          # extension → TOML
fimod s -i data.csv -e 'data' --output-format json        # explicit → JSON
fimod s -i users.json -e 'data' --output-format lines     # explicit → lines