Yq 4 53 3

yq 4.53.3

Overview

yq is a lightweight, portable command-line processor for YAML, JSON, XML, INI, TOML, HCL, CSV, TSV, Properties, Lua, Shell variables, and Base64. It uses jq-like expression syntax but works across all these formats. Written in Go — single binary, no dependencies.

Key capabilities:

• Read, update, delete, and create structured data via jq-style expressions
• In-place file editing (-i)
• Format conversion between any supported pair (YAML↔JSON, XML→YAML, TOML↔HCL, etc.)
• Multi-document YAML support
• Environment variable injection (env(), strenv(), envsubst())
• File loading (load(), load_xml(), load_props())
• Comment and anchor/alias preservation during edits
• Reduce/merge across multiple files with eval-all

Usage

Basic syntax

yq [flags] 'expression' [file ...]
yq [flags] 'expression' < file          # pipe from stdin
yq -n 'expression'                       # no input, create from scratch

Common operations

Read a value:

yq '.a.b[0].c' file.yaml

Update in place:

yq -i '.a.b[0].c = "cool"' file.yaml

Use environment variables:

NAME=mike yq -i '.a.b[0].c = strenv(NAME)' file.yaml

Multiple updates in one pass:

yq -i '.a = "x" | .b.c = "y"' file.yaml

Find and update in an array:

yq -i '(.[] | select(.name == "foo") | .address) = "12 cat st"' data.yaml

Convert formats:

yq -Poy sample.json    # JSON → pretty YAML
yq -o json file.yaml   # YAML → JSON
yq -o yaml file.xml    # XML → YAML

Merge multiple files:

yq -n 'load("a.yaml") * load("b.yaml")'
yq ea '. as $item ireduce ({}; . * $item)' path/*.yml

Create from scratch:

yq -n '.a.b = "cat" | .x = "frog"'

Key flags

Expression commands

yq eval 'expr' file.yaml      # default: process each document in sequence
yq eval-all 'expr' file.yaml  # load all docs from all files, run once (alias: yq ea)

Gotchas

• PowerShell quoting — use single quotes for expressions, or escape double quotes. PowerShell expands $() and "" inside strings.
• Bash trailing newlines — $(cmd) strips trailing newlines. Use printf -v var "text\n" or multiline assignment to preserve them in YAML blocks.
• Merge anchor legacy behavior — by default, yq uses non-spec merge anchor semantics (later anchors override earlier ones). Add --yaml-fix-merge-anchor-to-spec for correct YAML 1.2 behavior (earlier keys win).
• yes/no are not booleans — YAML 1.2 dropped them as boolean values. They parse as strings.
• Comment preservation is imperfect — yq tries to preserve comments and whitespace during edits, but complex restructures may lose them.
• In-place editing (-i) writes to the first file argument only. Subsequent files are read-only inputs.
• env() parses YAML — env(VAR) interprets the value as YAML (so "true" becomes boolean). Use strenv(VAR) for raw strings.
• Numeric keys — .0 traverses array index 0; use .["0"] to access a map key that is literally the string "0".
• Security flags — use --security-disable-env-ops and --security-disable-file-ops when processing untrusted expressions.

References

• 01-traverse-read — Path navigation, splat, wildcards, dynamic keys
• 02-assign-update — =, |=, create nodes, update in place
• 03-select-filter — select(), filter, boolean and comparison operators
• 04-reduce-merge — ireduce, merge files, collect into arrays/objects
• 05-format-conversion — Convert between YAML, JSON, XML, TOML, HCL, CSV, INI, Properties, Lua, Shell
• 06-string-operators — Regex (test, match, capture, sub), interpolation, slicing
• 07-env-file-operators — env(), strenv(), envsubst(), load(), file operations
• 08-datetime — Date/time parsing, formatting, timezone handling
• 09-advanced-features — Comments, style, tags, anchors/aliases, entries, path