### Install YAML v3 Package

Source: https://github.com/google/yamlfmt/blob/main/pkg/yaml/README.md

Use 'go get' to install the YAML v3 package. This command fetches and installs the specified package.

```bash
go get gopkg.in/yaml.v3
```

--------------------------------

### yamlfmt Configuration File Example

Source: https://context7.com/google/yamlfmt/llms.txt

Example `.yamlfmt` configuration file demonstrating command-level, path, regex exclude, extensions, and formatter settings.

```yaml
# .yamlfmt
# Command configuration
line_ending: lf
doublestar: false
continue_on_error: false
match_type: standard
gitignore_excludes: true
gitignore_path: .gitignore
output_format: default

# Path configuration
include:
  - ./config/
  - ./manifests/
exclude:
  - ./vendor/
  - ./node_modules/
  - ./.git/

# Regex exclude patterns (exclude files by content)
regex_exclude:
  - "^# DO NOT FORMAT"

# Extensions to include (standard mode only)
extensions:
  - yaml
  - yml

# Formatter configuration
formatter:
  type: basic
  indent: 2
  include_document_start: true
  line_ending: lf
  retain_line_breaks: false
  max_line_length: 120
  indentless_arrays: false
  pad_line_comments: 2
  trim_trailing_whitespace: true
  eof_newline: true
```

--------------------------------

### Basic Formatter Configuration Example

Source: https://context7.com/google/yamlfmt/llms.txt

This is a comprehensive example of a .yamlfmt configuration file, demonstrating various options for indentation, document structure, line handling, comments, and advanced settings.

```yaml
formatter:
  type: basic

  # Indentation
  indent: 2
  array_indent: 2
  indent_root_array: false
  indentless_arrays: false

  # Document structure
  include_document_start: true      # Add --- at document start
  line_ending: lf                   # lf or crlf
  max_line_length: 80               # 0 for no limit

  # Line handling
  retain_line_breaks: false
  retain_line_breaks_single: false  # Keep single blank lines
  trim_trailing_whitespace: true
  eof_newline: true

  # Comments
  pad_line_comments: 1              # Spaces before line comments

  # Advanced options
  scan_folded_as_literal: false     # Preserve newlines in folded blocks
  disallow_anchors: false           # Reject YAML anchors/aliases
  drop_merge_tag: false             # Drop !!merge from merge operations
  strip_directives: false           # Handle YAML directives
  disable_alias_key_correction: false

  # Style forcing
  force_array_style: ""             # "flow", "block", or empty
  force_quote_style: ""             # "single", "double", or empty

```

--------------------------------

### Gitignore Patterns File Example

Source: https://context7.com/google/yamlfmt/llms.txt

Example content for a gitignore-style patterns file used with `match_type: gitignore`.

```bash
*.yaml
*.yml
!testdata/
!vendor/

```

--------------------------------

### Basic Formatter with Include Document Start

Source: https://github.com/google/yamlfmt/blob/main/docs/config-file.md

Configure the basic formatter to include the document start marker.

```yaml
formatter:
  type: basic
  include_document_start: true
```

--------------------------------

### Install yamlfmt using Go

Source: https://github.com/google/yamlfmt/blob/main/README.md

Install the yamlfmt command-line tool using Go. Requires Go version 1.21 or greater.

```bash
go install github.com/google/yamlfmt/cmd/yamlfmt@latest
```

--------------------------------

### GitLab CI Integration Example

Source: https://github.com/google/yamlfmt/blob/main/docs/output.md

Example configuration for a GitLab CI pipeline to run yamlfmt and generate a Code Quality report artifact. Ensure 'yamlfmt-report' is the correct filename.

```yaml
yamlfmt:
  script:
    - yamlfmt -dry -output_format gitlab . >yamlfmt-report
  artifacts:
    when: always
    reports:
      codequality: yamlfmt-report
```

--------------------------------

### Print Version Information

Source: https://github.com/google/yamlfmt/blob/main/docs/command-usage.md

Display the installed yamlfmt version using the '-version' flag.

```bash
yamlfmt -version
```

--------------------------------

### String Array Flag Examples

Source: https://github.com/google/yamlfmt/blob/main/docs/command-usage.md

Demonstrates the two ways to provide values for string array flags: individual flags or a single comma-separated flag.

```bash
-arrFlag a -arrFlag b -arrFlag c
```

```bash
-arrFlag a,b,c
```

```bash
-arrFlag a,b -arrFlag c
```

--------------------------------

### Default Output Format

Source: https://github.com/google/yamlfmt/blob/main/docs/output.md

Shows the default diff format when differences are found. No specific setup is required.

```text
The following formatting differences were found:

y.yaml:
  a:     a:
-  b: 1    b: 1
+
z.yaml:
  a:     a:
-  b: 1    b: 1
+
x.yaml:
  a:     a:
-  b: 1    b: 1
+
```

--------------------------------

### GitLab CI Basic Usage

Source: https://context7.com/google/yamlfmt/llms.txt

Example GitLab CI configuration to run yamlfmt on all YAML files in the repository.

```yaml
yamlfmt:
  image: ghcr.io/google/yamlfmt:latest
  script:
    - yamlfmt -lint .

```

--------------------------------

### Extract and Run yamlfmt

Source: https://context7.com/google/yamlfmt/llms.txt

Extract the yamlfmt binary from its archive and verify its installation by checking the version.

```bash
tar -xzf "yamlfmt_${VERSION}_Linux_x86_64.tar.gz"
./yamlfmt -version
```

--------------------------------

### GitLab CI job for yamlfmt linting

Source: https://github.com/google/yamlfmt/blob/main/README.md

Example GitLab CI job configuration to use the yamlfmt Docker image for linting YAML files.

```yaml
yamllint:
  image: ghcr.io/google/yamlfmt:latest
  script:
    - yamlfmt -lint .
```

--------------------------------

### Run yamlfmt on custom file types

Source: https://github.com/google/yamlfmt/blob/main/docs/pre-commit.md

Override the default behavior to run yamlfmt on specific file types by configuring the 'types' and 'files' options. This example uses a placeholder regex for file paths.

```yaml
- repo: https://github.com/google/yamlfmt
  rev: v0.19.0
  hooks:
    - id: yamlfmt
      types: [file]
      files: <filepath regex>

```

--------------------------------

### Print Help Information

Source: https://github.com/google/yamlfmt/blob/main/docs/command-usage.md

Display command usage information by using the '-help' flag.

```bash
yamlfmt -help
```

--------------------------------

### Provide Formatter Configuration

Source: https://github.com/google/yamlfmt/blob/main/docs/command-usage.md

Use the `-formatter` flag with comma-separated `key=value` pairs to provide specific formatter configurations. Refer to documentation for available options.

```bash
yamlfmt -formatter indent=2,include_document_start=true
```

--------------------------------

### Print Version and Configuration

Source: https://context7.com/google/yamlfmt/llms.txt

Display the current yamlfmt version using -version or print the effective configuration using -print_conf.

```bash
yamlfmt -version

```

```bash
yamlfmt -print_conf

```

--------------------------------

### Use Global Config

Source: https://context7.com/google/yamlfmt/llms.txt

Use the -global_conf flag to enable the use of the global system-wide configuration file.

```bash
yamlfmt -global_conf .

```

--------------------------------

### Basic Formatter Configuration

Source: https://github.com/google/yamlfmt/blob/main/docs/config-file.md

Use this configuration to set up the default basic formatter.

```yaml
formatter:
  type: basic
```

--------------------------------

### Format a Single YAML File

Source: https://github.com/google/yamlfmt/blob/main/docs/command-usage.md

Use the default configuration to format a single YAML file.

```bash
yamlfmt x.yaml
```

--------------------------------

### Create New Integration Test Case

Source: https://github.com/google/yamlfmt/blob/main/docs/integration-test.md

Scaffolds a new integration test by creating the necessary directory structure and Go test file. You will need to manually add input files and expected output.

```shell
TESTNAME=my_new_test make command_test_case
```

--------------------------------

### Format YAML files with default settings

Source: https://github.com/google/yamlfmt/blob/main/README.md

Run the yamlfmt tool with default settings, providing one or more file paths as arguments.

```bash
yamlfmt x.yaml y.yaml <...>
```

--------------------------------

### Specify Configuration File Path

Source: https://github.com/google/yamlfmt/blob/main/docs/command-usage.md

Use the `-conf` flag to specify a path to a custom configuration file.

```bash
yamlfmt -conf ./config/.yamlfmt
```

--------------------------------

### Docker Container Basic Usage

Source: https://context7.com/google/yamlfmt/llms.txt

Run yamlfmt using the official Docker container by mounting the current directory to '/project'.

```bash
# Basic usage - mount current directory
docker run -v "$(pwd):/project" ghcr.io/google/yamlfmt:latest .

```

--------------------------------

### Line Output Format

Source: https://github.com/google/yamlfmt/blob/main/docs/output.md

Displays a concise list of files with formatting differences. Useful for a quick overview.

```text
x.yaml: formatting difference found
y.yaml: formatting difference found
z.yaml: formatting difference found
```

--------------------------------

### Uncompress and run yamlfmt binary

Source: https://github.com/google/yamlfmt/blob/main/README.md

After successful checksum validation, uncompress the downloaded archive and run the yamlfmt binary.

```bash
tar -xzf yamlfmt_A.B.C_Linux_x86_64.tar.gz
./yamlfmt
```

--------------------------------

### Use system-installed yamlfmt with pre-commit

Source: https://github.com/google/yamlfmt/blob/main/docs/pre-commit.md

Configure the pre-commit hook to use a system-installed yamlfmt binary by setting the language to 'system'. Ensure yamlfmt is in your PATH.

```yaml
- repo: https://github.com/google/yamlfmt
  rev: v0.19.0
  hooks:
    - id: yamlfmt
      language: system

```

--------------------------------

### Download release artifacts for verification

Source: https://github.com/google/yamlfmt/blob/main/README.md

Download necessary files (checksums, signature, certificate) from a specific release version for artifact verification.

```text
curl -sfLO https://github.com/google/yamlfmt/releases/download/vA.B.C/checksums.txt
curl -sfLO https://github.com/google/yamlfmt/releases/download/vA.B.C/checksums.txt.pem
curl -sfLO https://github.com/google/yamlfmt/releases/download/vA.B.C/checksums.txt.sig
```

--------------------------------

### Enable Global Configuration

Source: https://github.com/google/yamlfmt/blob/main/docs/command-usage.md

Use the `-global_conf` flag to force yamlfmt to use the system-wide configuration file.

```bash
yamlfmt -global_conf
```

--------------------------------

### Print Merged Configuration

Source: https://github.com/google/yamlfmt/blob/main/docs/command-usage.md

View the effective merged configuration by using the '-print_conf' flag.

```bash
yamlfmt -print_conf
```

--------------------------------

### Verify Release Artifacts with Cosign

Source: https://context7.com/google/yamlfmt/llms.txt

Verify the authenticity of downloaded yamlfmt binaries using `cosign`. This process involves downloading checksums, signatures, and certificates, then using `cosign verify-blob`.

```bash
# Download release artifacts (replace A.B.C with version)
VERSION="0.19.0"

curl -sfLO "https://github.com/google/yamlfmt/releases/download/v${VERSION}/checksums.txt"
curl -sfLO "https://github.com/google/yamlfmt/releases/download/v${VERSION}/checksums.txt.pem"
curl -sfLO "https://github.com/google/yamlfmt/releases/download/v${VERSION}/checksums.txt.sig"

# Verify signature with cosign
cosign verify-blob checksums.txt \
    --certificate checksums.txt.pem \
    --signature checksums.txt.sig \
    --certificate-identity-regexp 'https://github\.com/google/yamlfmt/\.github/workflows/.+' \
    --certificate-oidc-issuer "https://token.actions.githubusercontent.com"

# Download and verify the binary
curl -sfLO "https://github.com/google/yamlfmt/releases/download/v${VERSION}/yamlfmt_${VERSION}_Linux_x86_64.tar.gz"
sha256sum --ignore-missing -c checksums.txt
```

--------------------------------

### Format YAML files using doublestar globs

Source: https://github.com/google/yamlfmt/blob/main/README.md

Use the `-dstar` flag to enable an alternate mode that searches paths using doublestar globs for YAML files.

```bash
yamlfmt -dstar **/*.{yaml,yml}
```

--------------------------------

### Add Custom Extensions

Source: https://context7.com/google/yamlfmt/llms.txt

Use the -extensions flag to include additional file extensions for formatting, particularly useful in standard mode.

```bash
yamlfmt -extensions yaml.gotmpl .

```

--------------------------------

### Set Output Format

Source: https://github.com/google/yamlfmt/blob/main/docs/command-usage.md

Use the `-output_format` flag to choose a different output format, such as `line`. Defaults to `default`. See output documentation for details.

```bash
yamlfmt -output_format line
```

--------------------------------

### Formatter Configuration via Flags

Source: https://context7.com/google/yamlfmt/llms.txt

Override specific formatter settings directly from the command line using the -formatter flag.

```bash
yamlfmt -formatter indent=4,include_document_start=true .

```

```bash
yamlfmt -formatter retain_line_breaks=true,max_line_length=100 .

```

--------------------------------

### Run Integration Tests

Source: https://github.com/google/yamlfmt/blob/main/docs/integration-test.md

Execute all integration tests for yamlfmt. This command builds and runs the end-to-end tests.

```shell
make integrationtest
```

--------------------------------

### Docker Container with Custom Config File

Source: https://context7.com/google/yamlfmt/llms.txt

Use a custom configuration file with the Docker container by specifying its path with the -conf flag.

```bash
# With custom config file
docker run -v "$(pwd):/project" ghcr.io/google/yamlfmt:latest -conf .yamlfmt .

```

--------------------------------

### Docker Container Format Specific Files

Source: https://context7.com/google/yamlfmt/llms.txt

Format specific YAML files by providing their names as arguments to the Docker container command.

```bash
# Format specific files
docker run -v "$(pwd):/project" ghcr.io/google/yamlfmt:latest config.yaml

```

--------------------------------

### Debug Logging Options

Source: https://context7.com/google/yamlfmt/llms.txt

Enable detailed debug logging for specific components or all components using the -debug flag.

```bash
yamlfmt -debug paths .

```

```bash
yamlfmt -debug config .

```

```bash
yamlfmt -debug diffs .

```

```bash
yamlfmt -debug all .

```

--------------------------------

### Use KYAML Formatter

Source: https://context7.com/google/yamlfmt/llms.txt

Specify the KYAML formatter to be used via the -kyaml flag.

```bash
yamlfmt -kyaml .

```

--------------------------------

### Enable All Debug Codes

Source: https://github.com/google/yamlfmt/blob/main/docs/command-usage.md

Use the `-debug all` flag to enable all available debug logging codes.

```bash
yamlfmt -debug all
```

--------------------------------

### Format YAML Files

Source: https://context7.com/google/yamlfmt/llms.txt

Format one or more YAML files by providing their paths as arguments. Supports recursive formatting and pattern matching.

```bash
# Format a single file
yamlfmt config.yaml
```

```bash
# Format multiple files
yamlfmt config.yaml deployment.yaml values.yaml
```

```bash
# Format all YAML files in a directory recursively
yamlfmt .
```

```bash
# Format files matching specific patterns (doublestar mode)
yamlfmt -dstar "**/*.yaml"
```

```bash
# Format only specific subdirectories
yamlfmt ./config/ ./manifests/
```

--------------------------------

### Format YAML files in a directory recursively

Source: https://github.com/google/yamlfmt/blob/main/README.md

Format all YAML files within a specified directory, searching recursively.

```bash
yamlfmt .
```

--------------------------------

### Output Format Options

Source: https://context7.com/google/yamlfmt/llms.txt

Control the output format using -output_format. Use 'line' for line-based output or 'gitlab' for GitLab CI Code Quality report format. The -dry flag performs a dry run.

```bash
yamlfmt -output_format line -dry .

```

```bash
yamlfmt -output_format gitlab -dry . > report.json

```

--------------------------------

### Run yamlfmt using Docker

Source: https://github.com/google/yamlfmt/blob/main/README.md

Execute the yamlfmt command within a Docker container, mounting the current directory as a volume.

```bash
docker run -v "$(pwd):/project" ghcr.io/google/yamlfmt:latest <yamlfmt args>
```

--------------------------------

### Docker Container Format from Stdin

Source: https://context7.com/google/yamlfmt/llms.txt

Format YAML content piped to the Docker container's standard input using the -in flag.

```bash
# Format from stdin
cat config.yaml | docker run -i ghcr.io/google/yamlfmt:latest -in

```

--------------------------------

### Download and validate release archive checksum

Source: https://github.com/google/yamlfmt/blob/main/README.md

Download a specific release archive and validate its checksum against the downloaded checksums file.

```bash
curl -sfLO https://github.com/google/yamlfmt/releases/download/vA.B.C/yamlfmt_A.B.C_Linux_x86_64.tar.gz
sha256sum --ignore-missing -c checksums.txt
```

--------------------------------

### Use Formatter Registry in Go

Source: https://context7.com/google/yamlfmt/llms.txt

Manage multiple yamlfmt formatter types using a registry. This allows for dynamic selection and use of different formatting strategies within your Go application.

```go
// Using the formatter registry for multiple formatter types
package main

import (
    "fmt"
    "log"

    "github.com/google/yamlfmt"
    "github.com/google/yamlfmt/formatters/basic"
    "github.com/google/yamlfmt/formatters/kyaml"
)

func main() {
    // Create registry with default formatter
    registry := yamlfmt.NewFormatterRegistry(&basic.BasicFormatterFactory{})

    // Add additional formatters
    registry.Add(&kyaml.KyamlFormatterFactory{})

    // Get factory by type
    factory, err := registry.GetFactory("basic")
    if err != nil {
        log.Fatalf("failed to get factory: %v", err)
    }

    // Get default factory
    defaultFactory, err := registry.GetDefaultFactory()
    if err != nil {
        log.Fatalf("failed to get default factory: %v", err)
    }

    fmt.Printf("Factory type: %s\n", factory.Type())
    fmt.Printf("Default factory type: %s\n", defaultFactory.Type())
}
```

--------------------------------

### Format YAML Files with Doublestar Globbing

Source: https://github.com/google/yamlfmt/blob/main/docs/command-usage.md

Utilize doube-star globbing for more dynamic path patterns to select files for formatting.

```bash
yamlfmt -dstar "**/*.yaml"
```

--------------------------------

### Enable Doublestar Mode via Flag

Source: https://context7.com/google/yamlfmt/llms.txt

Override the default path collection mode to 'doublestar' using the -match_type or -dstar flag.

```bash
yamlfmt -match_type doublestar "**/*.yaml"

```

```bash
yamlfmt -dstar "**/*.yaml"

```

--------------------------------

### Format YAML with Basic Formatter in Go

Source: https://context7.com/google/yamlfmt/llms.txt

Use the basic formatter to programmatically format YAML content within your Go applications. Configure settings like indentation and line endings.

```go
package main

import (
    "fmt"
    "log"

    "github.com/google/yamlfmt"
    "github.com/google/yamlfmt/formatters/basic"
)

func main() {
    // Create a formatter factory
    factory := &basic.BasicFormatterFactory{}

    // Configure formatter settings
    config := map[string]interface{}{
        "indent":                 2,
        "include_document_start": true,
        "line_ending":           "lf",
        "retain_line_breaks":    false,
        "pad_line_comments":     2,
    }

    // Create the formatter
    formatter, err := factory.NewFormatter(config)
    if err != nil {
        log.Fatalf("failed to create formatter: %v", err)
    }

    // Input YAML content
    input := []byte(`foo:   bar
baz:    qux
items:
  - one
  - two`)

    // Format the content
    output, err := formatter.Format(input)
    if err != nil {
        log.Fatalf("failed to format: %v", err)
    }

    fmt.Printf("Formatted output:\n%s", output)
    // Output:
    // ---
    // foo: bar
    // baz: qux
    // items:
    //   - one
    //   - two
}
```

--------------------------------

### Lint YAML Files for Formatting Differences

Source: https://github.com/google/yamlfmt/blob/main/docs/command-usage.md

Use Lint mode with the '-lint' flag. This mode checks for formatting differences and exits with code 1 if any are found, outputting diffs to stdout.

```bash
yamlfmt -lint .
```

--------------------------------

### Specify Custom Config File Location

Source: https://context7.com/google/yamlfmt/llms.txt

Use the -conf flag to specify a custom path for the yamlfmt configuration file.

```bash
yamlfmt -conf ./config/.yamlfmt .

```

--------------------------------

### Dry Run YAML Formatting

Source: https://context7.com/google/yamlfmt/llms.txt

Preview formatting changes without modifying files. Displays diffs for files that would be altered. Supports quiet mode.

```bash
# Dry run on all YAML files
yamlfmt -dry .
```

```bash
# Dry run with quiet mode (only file paths)
yamlfmt -dry -quiet .
```

```bash
# Dry run on specific files
yamlfmt -dry config.yaml
```

```bash
# Example output:
# config.yaml:
#   foo:     foo:
# -  bar: 1    bar: 1
# +
```

--------------------------------

### Verify signature of release artifacts

Source: https://github.com/google/yamlfmt/blob/main/README.md

Verify the signature of the checksums file using cosign, specifying certificate identity and OIDC issuer.

```shell
cosign verify-blob checksums.txt \
   --certificate checksums.txt.pem \
   --signature checksums.txt.sig \
   --certificate-identity-regexp 'https://github\.com/google/yamlfmt/\.github/workflows/.+' \
   --certificate-oidc-issuer "https://token.actions.githubusercontent.com"
```

--------------------------------

### Unmarshal and Marshal YAML Data in Go

Source: https://github.com/google/yamlfmt/blob/main/pkg/yaml/README.md

Demonstrates unmarshalling YAML data into a struct and a map, then marshalling them back to YAML. Ensure struct fields are public for correct unmarshalling. The `yaml:"flow"` tag controls the output format for slices.

```Go
package main

import (
        "fmt"
        "log"

        "gopkg.in/yaml.v3"
)

var data = `
a: Easy!
b:
  c: 2
  d: [3, 4]
`

// Note: struct fields must be public in order for unmarshal to
// correctly populate the data.
type T struct {
        A string
        B struct {
                RenamedC int   `yaml:"c"`
                D        []int `yaml:",flow"`
        }
}

func main() {
        t := T{}
    
        err := yaml.Unmarshal([]byte(data), &t)
        if err != nil {
                log.Fatalf("error: %v", err)
        }
        fmt.Printf("--- t:\n%v\n\n", t)
    
        d, err := yaml.Marshal(&t)
        if err != nil {
                log.Fatalf("error: %v", err)
        }
        fmt.Printf("--- t dump:\n%s\n\n", string(d))
    
        m := make(map[interface{}]interface{})
    
        err = yaml.Unmarshal([]byte(data), &m)
        if err != nil {
                log.Fatalf("error: %v", err)
        }
        fmt.Printf("--- m:\n%v\n\n", m)
    
        d, err = yaml.Marshal(&m)
        if err != nil {
                log.Fatalf("error: %v", err)
        }
        fmt.Printf("--- m dump:\n%s\n\n", string(d))
}
```

--------------------------------

### Pre-commit Hook with System-Installed yamlfmt

Source: https://context7.com/google/yamlfmt/llms.txt

Configure the pre-commit hook to use a system-installed version of yamlfmt by setting the language to 'system'.

```yaml
# .pre-commit-config.yaml

# Use system-installed yamlfmt
- repo: https://github.com/google/yamlfmt
  rev: v0.19.0
  hooks:
    - id: yamlfmt
      language: system

```

--------------------------------

### Use Gitignore for Excludes

Source: https://github.com/google/yamlfmt/blob/main/docs/command-usage.md

Enable the `-gitignore_excludes` flag to use a `.gitignore` file for excluding paths. This is in addition to other exclude patterns.

```bash
yamlfmt -gitignore_excludes
```

--------------------------------

### Enable Debug Logging

Source: https://github.com/google/yamlfmt/blob/main/docs/command-usage.md

Use the `-debug` flag with comma-separated codes to enable specific debug logging categories. See Debug Logging section for supported codes.

```bash
yamlfmt -debug paths,config
```

--------------------------------

### Kyaml Formatter Configuration

Source: https://github.com/google/yamlfmt/blob/main/docs/config-file.md

Switch to the kyaml formatter by changing the type in the formatter configuration.

```yaml
formatter:
  type: kyaml
```

--------------------------------

### Enable KYAML Formatter

Source: https://github.com/google/yamlfmt/blob/main/docs/command-usage.md

Use the `-kyaml` flag to enable the alternate KYAML formatter. This overrides any formatter configuration from a detected config file.

```bash
yamlfmat -kyaml
```

--------------------------------

### Dry Run Formatting Differences

Source: https://github.com/google/yamlfmt/blob/main/docs/command-usage.md

Enable Dry Run mode using the '-dry' flag. This mode formats files and prints any files that would have had a formatting diff to stdout.

```bash
yamlfmt -dry .
```

--------------------------------

### Pre-commit Hook with Custom File Types

Source: https://context7.com/google/yamlfmt/llms.txt

Customize the file types and patterns that the pre-commit hook will process by specifying 'types' and 'files'.

```yaml
# .pre-commit-config.yaml

# Custom file types
- repo: https://github.com/google/yamlfmt
  rev: v0.19.0
  hooks:
    - id: yamlfmt
      types: [file]
      files: \.(yaml|yml|yaml\.gotmpl)$

```

--------------------------------

### Pre-commit Hook with Configuration File

Source: https://context7.com/google/yamlfmt/llms.txt

Configure the pre-commit hook to use a specific configuration file and disable passing filenames to yamlfmt.

```yaml
# .pre-commit-config.yaml

# Use with configuration file (disable passing filenames)
- repo: https://github.com/google/yamlfmt
  rev: v0.19.0
  hooks:
    - id: yamlfmt
      pass_filenames: false

```

--------------------------------

### Format YAML from Stdin

Source: https://github.com/google/yamlfmt/blob/main/docs/command-usage.md

Read YAML input from stdin and write the formatted output to stdout. This can be achieved using '-', '/dev/stdin', or the '-in' flag.

```bash
cat x.yaml | yamlfmt -
```

```bash
cat x.yaml | yamlfmt /dev/stdin
```

```bash
cat x.yaml | yamlfmt -in
```

--------------------------------

### Standard Path Collection Mode

Source: https://context7.com/google/yamlfmt/llms.txt

Configure yamlfmt to use standard file and directory path matching. This is the default mode and is suitable for direct path specifications.

```yaml
# .yamlfmt
match_type: standard
include:
  - ./config/
  - ./manifests/
exclude:
  - ./test/fixtures/
extensions:
  - yaml
  - yml

```

--------------------------------

### Specify File Extensions

Source: https://github.com/google/yamlfmt/blob/main/docs/command-usage.md

Use the `-extensions` flag with comma-separated values to define file extensions for standard path collection. This has no effect in Doublestar mode.

```bash
yamlfmt -extensions yaml,yml
```

--------------------------------

### yamlfmt Dry Run with Different Output Formats

Source: https://context7.com/google/yamlfmt/llms.txt

Utilize the `yamlfmt -dry` command to check for formatting differences. Supports various output formats like default (diff), line, and GitLab Code Quality report for CI/CD integration.

```bash
# Default output - shows side-by-side diff
yamlfmt -dry .
# Output:
# config.yaml:
#   foo:     foo:
# -  bar: 1    bar: 1
# +

# Line output - simple one-line-per-file format
yamlfmt -dry -output_format line .
# Output:
# config.yaml: formatting difference found
# deployment.yaml: formatting difference found

# GitLab Code Quality report format
yamlfmt -dry -output_format gitlab .
# Output:
# [
#   {
#     "description": "Not formatted correctly, run yamlfmt to resolve.",
#     "check_name": "yamlfmt",
#     "fingerprint": "c1dddeed9a8423b815cef59434fe3dea90d946016c8f71ecbd7eb46c528c0179",
#     "severity": "major",
#     "location": {
#       "path": "config.yaml"
#     }
#   }
# ]

# Compact GitLab output with quiet mode
yamlfmt -dry -output_format gitlab -quiet . > report.json
```

--------------------------------

### Verbose Mode in Format

Source: https://github.com/google/yamlfmt/blob/main/docs/command-usage.md

Enable verbose mode with '-verbose' or '-v'. This flag only affects the Format mode, providing more detailed output.

```bash
yamlfmt -v .
```

--------------------------------

### GitLab CI with Code Quality Report

Source: https://context7.com/google/yamlfmt/llms.txt

Configure GitLab CI to use yamlfmt in dry run mode with 'gitlab' output format to generate a Code Quality report.

```yaml
yamlfmt:
  image: ghcr.io/google/yamlfmt:latest
  script:
    - yamlfmt -dry -output_format gitlab . > yamlfmt-report.json
  artifacts:
    when: always
    reports:
      codequality: yamlfmt-report.json

```

--------------------------------

### Add Exclude Patterns from Command Line

Source: https://context7.com/google/yamlfmt/llms.txt

Specify exclude patterns directly on the command line using the -exclude flag.

```bash
yamlfmt -exclude ./vendor/,./node_modules/ .

```

--------------------------------

### Process YAML via Stdin/Stdout

Source: https://context7.com/google/yamlfmt/llms.txt

Read YAML from stdin and output formatted YAML to stdout. Useful for pipeline integration. Triggered by '-', '/dev/stdin', or '-in'.

```bash
# Using dash notation
cat unformatted.yaml | yamlfmt -
```

```bash
# Using /dev/stdin
cat unformatted.yaml | yamlfmt /dev/stdin
```

```bash
# Using -in flag
cat unformatted.yaml | yamlfmt -in
```

```bash
# Example with inline YAML
echo -e "foo:   bar\nbaz:    qux" | yamlfmt -
# Output:
# foo: bar
# baz: qux
```

```bash
# Pipe from kubectl and format
kubectl get configmap my-config -o yaml | yamlfmt -
```

--------------------------------

### Gitignore Path Collection Mode

Source: https://context7.com/google/yamlfmt/llms.txt

Configure yamlfmt to use patterns from a separate file, similar to .gitignore. This allows for complex exclusion rules.

```yaml
# .yamlfmt
match_type: gitignore
include:
  - yamlfmt.patterns  # File containing gitignore-style patterns

```

--------------------------------

### Disable Global Configuration

Source: https://github.com/google/yamlfmt/blob/main/docs/command-usage.md

Use the `-no_global_conf` flag to disable the use of the system-wide configuration file.

```bash
yamlfmt -no_global_conf
```

--------------------------------

### Specify Gitignore File Path

Source: https://github.com/google/yamlfmt/blob/main/docs/command-usage.md

Use the `-gitignore_path` flag to specify a custom path to a gitignore file. Defaults to `.gitignore`.

```bash
yamlfmt -gitignore_path .special_gitignore
```

--------------------------------

### Doublestar Path Collection Mode

Source: https://context7.com/google/yamlfmt/llms.txt

Configure yamlfmt to use glob patterns for file discovery. This mode is powerful for matching files recursively across directories.

```yaml
# .yamlfmt
match_type: doublestar
include:
  - "**/*.yaml"
  - "**/*.yml"
  - "config/**/*.yaml"
exclude:
  - "**/vendor/**"
  - "**/node_modules/**"
  - "**/*_test.yaml"

```

--------------------------------

### Lint YAML Files

Source: https://context7.com/google/yamlfmt/llms.txt

Check YAML files for formatting differences without modifying them. Exits with code 1 if changes are needed, suitable for CI checks. Supports quiet mode.

```bash
# Lint all YAML files in current directory
yamlfmt -lint .
```

```bash
# Lint specific files
yamlfmt -lint config.yaml deployment.yaml
```

```bash
# Lint with quiet mode (only show file paths)
yamlfmt -lint -quiet .
```

```bash
# Lint in doublestar mode
yamlfmt -dstar -lint "**/*.{yaml,yml}"
```

```bash
# Example CI/CD usage - fails if any files need formatting
yamlfmt -lint . || exit 1
```

--------------------------------

### GitLab Code Quality Report Format

Source: https://github.com/google/yamlfmt/blob/main/docs/output.md

Generates a JSON report for GitLab Code Quality. Requires the 'gitlab' output format.

```json
[
  {
    "description": "Not formatted correctly, run yamlfmt to resolve.",
    "check_name": "yamlfmt",
    "fingerprint": "c1dddeed9a8423b815cef59434fe3dea90d946016c8f71ecbd7eb46c528c0179",
    "severity": "major",
    "location": {
      "path": ".gitlab-ci.yml"
    }
  },
]
```

--------------------------------

### Set Match Type for Path Collection

Source: https://github.com/google/yamlfmt/blob/main/docs/command-usage.md

Use the `-match_type` flag to control how `include` and `exclude` patterns are interpreted. Refer to path documentation for details.

```bash
yamlfmt -match_type standard
```

--------------------------------

### Add yamlfmt to pre-commit config

Source: https://github.com/google/yamlfmt/blob/main/docs/pre-commit.md

Include this configuration in your .pre-commit-config.yaml to add yamlfmt as a pre-commit hook. This uses the default behavior of yamlfmt.

```yaml
- repo: https://github.com/google/yamlfmt
  rev: v0.19.0
  hooks:
    - id: yamlfmt

```

--------------------------------

### Verbose and Quiet Modes

Source: https://context7.com/google/yamlfmt/llms.txt

Control the verbosity of the output using -verbose for more details or -quiet (-q) for less output. Combine with -dry for dry run operations.

```bash
yamlfmt -verbose .

```

```bash
yamlfmt -dry -quiet .

```

```bash
yamlfmt -lint -q .

```

--------------------------------

### Docker Container Lint Mode

Source: https://context7.com/google/yamlfmt/llms.txt

Run yamlfmt in lint mode within the Docker container to check for formatting errors without modifying files.

```bash
# Lint mode
docker run -v "$(pwd):/project" ghcr.io/google/yamlfmt:latest -lint .

```

--------------------------------

### Exclude Paths from Collection

Source: https://github.com/google/yamlfmt/blob/main/docs/command-usage.md

Use the `-exclude` flag with comma-separated patterns to specify paths to exclude from collection. These are in addition to config file excludes.

```bash
yamlfmt -exclude ./not/,these_paths.yaml
```

--------------------------------

### Docker Container Dry Run

Source: https://context7.com/google/yamlfmt/llms.txt

Perform a dry run of yamlfmt within the Docker container to see which files would be modified, using the -dry flag.

```bash
# Dry run
docker run -v "$(pwd):/project" ghcr.io/google/yamlfmt:latest -dry .

```

--------------------------------

### Update Golden Files

Source: https://github.com/google/yamlfmt/blob/main/docs/integration-test.md

Regenerate the "golden" or expected output files used by the integration tests. This is useful after making changes to yamlfmt's behavior.

```shell
make integrationtest_update
```

--------------------------------

### Ignore File Metadata in yamlfmt

Source: https://github.com/google/yamlfmt/blob/main/docs/metadata.md

Add this metadata to a YAML file to exclude it from formatting by yamlfmt. Ensure the format is exactly `#!yamlfmt!:ignore` with no leading/trailing spaces.

```yaml
# !yamlfmt!:ignore
```

--------------------------------

### Quiet Mode in Dry Run or Lint

Source: https://github.com/google/yamlfmt/blob/main/docs/command-usage.md

Activate quiet mode using '-quiet' or '-q'. This flag only affects Dry Run or Lint modes, printing only the paths of files with diffs.

```bash
yamlfmt -dry -q .
```

--------------------------------

### File Modifications Report

Source: https://github.com/google/yamlfmt/blob/main/integrationtest/command/testdata/debug_diffs/stdout/stdout.txt

This output indicates which files were modified by the yamlfmt tool and shows the specific changes made. It is useful for reviewing formatting adjustments.

```text
[DEBUG]: The following files were modified:
a.yaml:
- a:  1  a: 1
+        
b.yaml:
- a:  1  a: 1
+        
c.yaml:
- a:  1  a: 1
+        
```

--------------------------------

### Run yamlfmt without passing filenames

Source: https://github.com/google/yamlfmt/blob/main/docs/pre-commit.md

Prevent the pre-commit hook from passing filenames as arguments by setting 'pass_filenames' to false. This ensures that path configurations in your .yamlfmt file are correctly applied.

```yaml
- repo: https://github.com/google/yamlfmt
  rev: v0.19.0
  hooks:
    - id: yamlfmt
      pass_filenames: false

```

--------------------------------

### Invalid Metadata Formats in yamlfmt

Source: https://github.com/google/yamlfmt/blob/main/docs/metadata.md

These formats will cause errors in yamlfmt. Ensure there is no space after the colon and that the identifier is correctly formatted.

```yaml
# !yamlfmt!: ignore
```

```yaml
# !yamlfmt!ignore
```

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