Docker Impl Go Templates

docker-impl-go-templates

Quick Reference

Go Template Syntax Basics

Template Functions

Critical Warnings

NEVER use double quotes around the entire --format value when it contains Go template double quotes inside -- ALWAYS use single quotes for the outer wrapper on Linux/macOS. On Windows PowerShell, use escaped double quotes or backticks.

NEVER omit {{ end }} when using {{ if }} or {{ range }} -- every conditional and loop block MUST be closed with {{ end }}.

NEVER assume a field exists without checking -- use {{ if .Field }} to guard against nil values that cause template execution errors.

ALWAYS use {{ json .Field }} instead of trying to manually format complex nested objects -- JSON output is reliable and pipeable to jq.

ALWAYS use table prefix with \t separators for readable multi-column output -- omitting table removes column headers.

---

Conditionals

if / else / end

# Simple conditional
docker inspect --format='{{if .State.Running}}UP{{else}}DOWN{{end}}' myapp

# Check for empty value
docker inspect --format='{{if .State.Health}}{{.State.Health.Status}}{{else}}no healthcheck{{end}}' myapp

# Nested conditional
docker inspect --format='{{if eq .State.Status "running"}}HEALTHY{{else if eq .State.Status "exited"}}STOPPED{{else}}UNKNOWN{{end}}' myapp

Comparison Functions

---

Range Loops

Iterating Over Arrays

# Environment variables (one per line)
docker inspect --format='{{range .Config.Env}}{{println .}}{{end}}' myapp

# Mounts with source and destination
docker inspect --format='{{range .Mounts}}{{.Source}} -> {{.Destination}}{{println}}{{end}}' myapp

Iterating Over Maps

# Network names and IPs
docker inspect --format='{{range $net, $conf := .NetworkSettings.Networks}}{{$net}}: {{$conf.IPAddress}}{{println}}{{end}}' myapp

# Port bindings
docker inspect --format='{{range $port, $bindings := .NetworkSettings.Ports}}{{$port}} -> {{(index $bindings 0).HostPort}}{{println}}{{end}}' myapp

# All labels
docker inspect --format='{{range $k, $v := .Config.Labels}}{{$k}}={{$v}}{{println}}{{end}}' myapp

Index Function

# First element of an array
docker inspect --format='{{index .Config.Cmd 0}}' myapp

# Specific port binding
docker inspect --format='{{(index (index .NetworkSettings.Ports "80/tcp") 0).HostPort}}' myapp

# Label by key (with dot in name)
docker inspect --format='{{index .Config.Labels "com.example.version"}}' myapp

---

Format Patterns by Command

docker inspect -- Container State (6 patterns)

# 1. Container status
docker inspect --format='{{.State.Status}}' CONTAINER

# 2. Container PID
docker inspect --format='{{.State.Pid}}' CONTAINER

# 3. Container start time
docker inspect --format='{{.State.StartedAt}}' CONTAINER

# 4. Container exit code
docker inspect --format='{{.State.ExitCode}}' CONTAINER

# 5. Running boolean
docker inspect --format='{{.State.Running}}' CONTAINER

# 6. Health check status
docker inspect --format='{{if .State.Health}}{{.State.Health.Status}}{{else}}none{{end}}' CONTAINER

docker inspect -- Network Info (6 patterns)

# 7. IP address (first network)
docker inspect --format='{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' CONTAINER

# 8. MAC address
docker inspect --format='{{range .NetworkSettings.Networks}}{{.MacAddress}}{{end}}' CONTAINER

# 9. All networks with IPs
docker inspect --format='{{range $k,$v := .NetworkSettings.Networks}}{{$k}}={{$v.IPAddress}} {{end}}' CONTAINER

# 10. Gateway
docker inspect --format='{{range .NetworkSettings.Networks}}{{.Gateway}}{{end}}' CONTAINER

# 11. Port bindings (all)
docker inspect --format='{{range $p,$conf := .NetworkSettings.Ports}}{{$p}}->{{(index $conf 0).HostPort}} {{end}}' CONTAINER

# 12. Specific port mapping
docker inspect --format='{{(index (index .NetworkSettings.Ports "80/tcp") 0).HostPort}}' CONTAINER

docker inspect -- Configuration (6 patterns)

# 13. Image name
docker inspect --format='{{.Config.Image}}' CONTAINER

# 14. Entrypoint
docker inspect --format='{{json .Config.Entrypoint}}' CONTAINER

# 15. Command
docker inspect --format='{{json .Config.Cmd}}' CONTAINER

# 16. Environment variables
docker inspect --format='{{range .Config.Env}}{{println .}}{{end}}' CONTAINER

# 17. All labels as JSON
docker inspect --format='{{json .Config.Labels}}' CONTAINER

# 18. Specific label
docker inspect --format='{{index .Config.Labels "com.example.version"}}' CONTAINER

docker inspect -- Mounts & Size (4 patterns)

# 19. All mounts as JSON
docker inspect --format='{{json .Mounts}}' CONTAINER

# 20. Mount sources and destinations
docker inspect --format='{{range .Mounts}}{{.Source}} -> {{.Destination}}{{println}}{{end}}' CONTAINER

# 21. Log file path
docker inspect --format='{{.LogPath}}' CONTAINER

# 22. Root filesystem size (requires -s flag)
docker inspect --size --format='{{.SizeRootFs}}' CONTAINER

docker ps (4 patterns)

# 23. Compact table
docker ps --format "table {{.Names}}\t{{.Image}}\t{{.Status}}\t{{.Ports}}"

# 24. Names only
docker ps --format "{{.Names}}"

# 25. With specific label
docker ps --format "table {{.Names}}\t{{.Label \"app\"}}\t{{.Status}}"

# 26. JSON output (one object per line)
docker ps --format json

docker images (3 patterns)

# 27. Compact image list
docker images --format "table {{.Repository}}\t{{.Tag}}\t{{.Size}}"

# 28. Repository:tag pairs
docker images --format "{{.Repository}}:{{.Tag}}"

# 29. With digest
docker images --digests --format "table {{.Repository}}\t{{.Tag}}\t{{.Digest}}"

docker stats / network / volume / system (5 patterns)

# 30. Stats with custom columns
docker stats --no-stream --format "table {{.Name}}\t{{.CPUPerc}}\t{{.MemUsage}}\t{{.NetIO}}"

# 31. Network listing
docker network ls --format "table {{.Name}}\t{{.Driver}}\t{{.Scope}}"

# 32. Volume listing
docker volume ls --format "table {{.Name}}\t{{.Driver}}\t{{.Mountpoint}}"

# 33. System disk usage
docker system df --format "table {{.Type}}\t{{.TotalCount}}\t{{.Size}}\t{{.Reclaimable}}"

# 34. Docker info field
docker info --format '{{.ServerVersion}}'

---

Scripting Patterns

Extract Values for Shell Scripts

# Get container ID by name
CID=$(docker ps -qf "name=myapp")

# Get IP address into variable
IP=$(docker inspect --format='{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' myapp)

# Get host port for container port 80
PORT=$(docker inspect --format='{{(index (index .NetworkSettings.Ports "80/tcp") 0).HostPort}}' myapp)

# Get all running container names
docker ps --format "{{.Names}}" | while read name; do
  echo "Container: $name"
done

# Get exit codes for all stopped containers
docker ps -a --filter status=exited --format "{{.Names}}: exit {{.Status}}"

Bulk Operations with Format Output

# Stop all containers on a specific network
docker network inspect --format='{{range .Containers}}{{.Name}} {{end}}' mynet | xargs docker stop

# Remove all images from a specific repository
docker images myrepo --format "{{.ID}}" | xargs docker rmi

# Get IPs of all running containers
docker ps -q | xargs -I {} docker inspect --format='{{.Name}}: {{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' {}

---

Decision Tree: Choosing Output Format

Need Docker command output?
├── Need full object details?
│   └── Use: docker inspect --format='{{json .}}' | jq
├── Need specific single field?
│   └── Use: --format='{{.Field.SubField}}'
├── Need readable multi-column table?
│   └── Use: --format "table {{.Col1}}\t{{.Col2}}"
├── Need machine-parseable output?
│   └── Use: --format json  OR  --format='{{json .Field}}'
├── Need to iterate nested data?
│   └── Use: --format='{{range .Items}}{{.Field}}{{println}}{{end}}'
└── Need conditional output?
    └── Use: --format='{{if .Cond}}yes{{else}}no{{end}}'

---

Reference Links

• references/patterns.md -- 30+ format patterns organized by Docker command
• references/examples.md -- Complex template examples with conditionals, range loops, and scripting
• references/anti-patterns.md -- Common Go template mistakes and how to fix them

Official Sources

• https://docs.docker.com/reference/cli/docker/inspect/
• https://docs.docker.com/reference/cli/docker/container/ls/
• https://docs.docker.com/reference/cli/docker/image/ls/
• https://pkg.go.dev/text/template

Go Template Anti-Patterns

Common mistakes when using Docker --format flags. Each anti-pattern includes the error,

WHY it fails, and the CORRECT alternative. Verified against Docker Engine 24+.

---

AP-01: Missing {{ end }} Closure

# WRONG -- missing {{ end }} causes parse error
docker inspect --format='{{if .State.Running}}UP' myapp
# Error: template: :1: unexpected EOF

# CORRECT -- ALWAYS close if/range blocks
docker inspect --format='{{if .State.Running}}UP{{end}}' myapp

WHY: Go templates require explicit block closure. Every {{ if }} and {{ range }} MUST have a matching {{ end }}.

---

AP-02: Quoting Conflict on Linux/macOS

# WRONG -- double quotes conflict with Go template syntax
docker inspect --format="{{.State.Status}}" myapp
# May work on some shells but breaks with nested quotes

# CORRECT -- ALWAYS use single quotes on Linux/macOS
docker inspect --format='{{.State.Status}}' myapp

WHY: The shell interprets double-quoted strings before Docker sees them. Backticks, dollar signs, and braces inside double quotes can trigger shell expansion. Single quotes pass the template verbatim.

---

AP-03: Accessing Nil/Missing Fields Without Guard

# WRONG -- crashes if no healthcheck is configured
docker inspect --format='{{.State.Health.Status}}' myapp
# Error: template: :1:... executing "..." at <.State.Health.Status>: nil pointer

# CORRECT -- guard with if
docker inspect --format='{{if .State.Health}}{{.State.Health.Status}}{{else}}none{{end}}' myapp

WHY: Not all containers have a healthcheck configured. .State.Health is nil when no HEALTHCHECK instruction exists. Accessing a field on a nil pointer causes a template execution error.

---

AP-04: Using Dot Notation for Labels with Dots

# WRONG -- Go interprets dots as field separators
docker inspect --format='{{.Config.Labels.com.docker.compose.project}}' myapp
# Error: template: :1:... can't evaluate field com in type ...

# CORRECT -- use index function for dotted key names
docker inspect --format='{{index .Config.Labels "com.docker.compose.project"}}' myapp

WHY: Go template dot notation (.field.subfield) treats each segment as a struct field. Label keys containing dots are map keys, not nested structs. ALWAYS use index to access map keys that contain dots.

---

AP-05: Forgetting table Keyword for Headers

# WRONG -- no headers, hard to read
docker ps --format "{{.Names}}\t{{.Status}}\t{{.Ports}}"
# Output:
# web    Up 2 hours    80/tcp
# db     Up 2 hours    5432/tcp

# CORRECT -- table prefix adds column headers
docker ps --format "table {{.Names}}\t{{.Status}}\t{{.Ports}}"
# Output:
# NAMES  STATUS        PORTS
# web    Up 2 hours    80/tcp
# db     Up 2 hours    5432/tcp

WHY: The table keyword is a Docker-specific extension (not standard Go templates). Without it, you get raw values only. ALWAYS use table when output is for human reading; omit it only for machine parsing.

---

AP-06: Using \t Without table for Alignment

# WRONG -- \t without table produces inconsistent alignment
docker ps --format "{{.Names}}\t{{.Image}}\t{{.Status}}"
# Output may not align because tab stops depend on terminal

# CORRECT for humans -- use table keyword
docker ps --format "table {{.Names}}\t{{.Image}}\t{{.Status}}"

# CORRECT for scripting -- use a fixed separator
docker ps --format "{{.Names}}|{{.Image}}|{{.Status}}"

WHY: Tab characters without the table directive rely on terminal tab stop settings. Different terminals and pipes handle tabs differently. For reliable alignment, ALWAYS use table. For machine parsing, use a deterministic separator like | or use --format json.

---

AP-07: Range Without Variable Assignment on Maps

# WRONG -- cannot access both key and value
docker inspect --format='{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' myapp
# Works but you lose the network name

# CORRECT -- assign key and value variables
docker inspect --format='{{range $name, $conf := .NetworkSettings.Networks}}{{$name}}: {{$conf.IPAddress}}{{println}}{{end}}' myapp

WHY: When iterating over maps, the simple {{ range }} form only gives you the value. To access both key and value, ALWAYS use the $key, $value := .Map assignment form.

---

AP-08: Assuming Port Bindings Always Exist

# WRONG -- crashes when port has no host binding
docker inspect --format='{{(index (index .NetworkSettings.Ports "80/tcp") 0).HostPort}}' myapp
# Error: index out of range when port is exposed but not published

# CORRECT -- guard against nil binding list
docker inspect --format='{{with index .NetworkSettings.Ports "80/tcp"}}{{(index . 0).HostPort}}{{else}}not published{{end}}' myapp

# ALSO CORRECT -- use if
docker inspect --format='{{if index .NetworkSettings.Ports "80/tcp"}}{{(index (index .NetworkSettings.Ports "80/tcp") 0).HostPort}}{{else}}not published{{end}}' myapp

WHY: A port can be EXPOSE'd in the Dockerfile without being published (-p). The binding list is nil or empty for unexposed ports. ALWAYS check before indexing into port binding arrays.

---

AP-09: Using json on Entire Inspect Without jq

# WRONG -- unreadable wall of JSON
docker inspect --format='{{json .}}' myapp
# Outputs thousands of characters on one line

# CORRECT -- pipe to jq for readability
docker inspect --format='{{json .}}' myapp | jq .

# BETTER -- target specific sections
docker inspect --format='{{json .State}}' myapp | jq .
docker inspect --format='{{json .NetworkSettings}}' myapp | jq .

WHY: {{ json . }} dumps the entire object as a single unformatted line. ALWAYS pipe to jq for human-readable output. Better yet, target a specific sub-object to reduce noise.

---

AP-10: Mixing Go Template and jq in --format

# WRONG -- jq syntax inside Go template
docker inspect --format='{{.Config.Labels | keys}}' myapp
# Error: function "keys" not defined

# CORRECT -- use json then pipe to jq
docker inspect --format='{{json .Config.Labels}}' myapp | jq 'keys'

WHY: Go templates and jq are separate languages. Go templates have a limited set of built-in functions (json, join, split, upper, lower, title, println, index, len). For complex JSON transformations, ALWAYS output JSON from Docker and process with jq.

---

AP-11: Forgetting println in Range Loops

# WRONG -- all values concatenated on one line
docker inspect --format='{{range .Config.Env}}{{.}}{{end}}' myapp
# Output: PATH=/usr/binHOME=/rootTERM=xterm

# CORRECT -- use println for line breaks
docker inspect --format='{{range .Config.Env}}{{println .}}{{end}}' myapp
# Output:
# PATH=/usr/bin
# HOME=/root
# TERM=xterm

WHY: Go templates do not insert newlines between range iterations. ALWAYS use {{ println . }} or {{ println }} at the end of range blocks to separate items.

---

AP-12: Using --format with docker inspect on Wrong Object Type

# WRONG -- using container fields on an image
docker inspect --format='{{.State.Status}}' nginx:latest
# Error: template: :1:... can't evaluate field State in type...

# CORRECT -- use image-specific fields
docker inspect --format='{{.Config.Cmd}}' nginx:latest
docker inspect --format='{{json .Config.ExposedPorts}}' nginx:latest

# CORRECT -- restrict type explicitly
docker inspect --type image --format='{{.RepoTags}}' nginx:latest
docker inspect --type container --format='{{.State.Status}}' myapp

WHY: docker inspect auto-detects object type, but container-specific fields (.State, .NetworkSettings, .HostConfig) do not exist on images. ALWAYS use --type when the object type is ambiguous, or know which fields belong to which object type.

---

AP-13: Hardcoding Container Names in Scripts

# WRONG -- breaks when container name changes
IP=$(docker inspect --format='{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' my-hardcoded-name)

# CORRECT -- use variables or docker ps filters
CONTAINER=$(docker ps -qf "label=app=web" | head -1)
IP=$(docker inspect --format='{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' "$CONTAINER")

# ALSO CORRECT -- use Compose service names
IP=$(docker inspect --format='{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' "$(docker compose ps -q web)")

WHY: Container names may change between deployments. ALWAYS use labels, filters, or Compose service lookups to find containers dynamically in scripts.

---

AP-14: Not Using --no-stream with docker stats in Scripts

# WRONG -- hangs forever in script (stats is a live stream)
CPU=$(docker stats --format "{{.CPUPerc}}" myapp)

# CORRECT -- use --no-stream for single snapshot
CPU=$(docker stats --no-stream --format "{{.CPUPerc}}" myapp)

WHY: docker stats continuously streams live data by default. In a script, this blocks indefinitely. ALWAYS use --no-stream when capturing stats output in variables or pipelines.

---

AP-15: Ignoring Platform Differences in Quoting

# Linux/macOS -- use single quotes
docker inspect --format='{{.State.Status}}' myapp

# Windows CMD -- use double quotes
docker inspect --format="{{.State.Status}}" myapp

# Windows PowerShell -- single quotes usually work
docker inspect --format='{{.State.Status}}' myapp

# WRONG -- escaping that works on one platform but not another
docker inspect --format=\"{{.State.Status}}\" myapp

WHY: Shell quoting rules differ across platforms. Single quotes on Linux/macOS prevent all shell interpolation. Windows CMD requires double quotes. PowerShell has its own rules. ALWAYS test format strings on your target platform.

---

Summary Table

Go Template Complex Examples

Advanced Go template patterns for Docker CLI. Each example is verified against Docker Engine 24+.

ALWAYS test complex templates on a single container before using in scripts.

---

Conditional Output Examples

Container Status Dashboard

# Color-coded status (for terminal output)
docker inspect --format='{{.Name}}: {{if eq .State.Status "running"}}RUNNING{{else if eq .State.Status "exited"}}EXITED (code {{.State.ExitCode}}){{else if eq .State.Status "paused"}}PAUSED{{else}}{{.State.Status}}{{end}}' CONTAINER

Health Check with Fallback

# Show health status or "no healthcheck configured"
docker inspect --format='{{if .State.Health}}Health: {{.State.Health.Status}} ({{len .State.Health.Log}} checks logged){{else}}Health: no healthcheck configured{{end}}' CONTAINER

Conditional Port Display

# Show port mappings only if they exist
docker inspect --format='{{if .NetworkSettings.Ports}}Ports: {{range $p, $conf := .NetworkSettings.Ports}}{{$p}}->{{if $conf}}{{(index $conf 0).HostPort}}{{else}}unmapped{{end}} {{end}}{{else}}No ports exposed{{end}}' CONTAINER

Memory Limit Check

# Show memory limit or "unlimited"
docker inspect --format='Memory: {{if eq .HostConfig.Memory 0}}unlimited{{else}}{{.HostConfig.Memory}} bytes{{end}}' CONTAINER

Non-Zero Exit Code Alert

# Alert on non-zero exit codes
docker inspect --format='{{if and (eq .State.Status "exited") (ne .State.ExitCode 0)}}ALERT: {{.Name}} exited with code {{.State.ExitCode}}{{end}}' CONTAINER

---

Range Loop Examples

Environment Variable Extraction

# All environment variables, one per line
docker inspect --format='{{range .Config.Env}}{{println .}}{{end}}' CONTAINER

# Filter-like: show env vars as KEY=VALUE (already in that format)
docker inspect --format='Environment:{{range .Config.Env}}
  {{.}}{{end}}' CONTAINER

Multi-Network Container Report

# Full network report for a container
docker inspect --format='Networks:{{range $name, $conf := .NetworkSettings.Networks}}
  {{$name}}:
    IP:      {{$conf.IPAddress}}
    Gateway: {{$conf.Gateway}}
    MAC:     {{$conf.MacAddress}}{{end}}' CONTAINER

Mount Summary

# All mounts with type, source, destination, and mode
docker inspect --format='Mounts:{{range .Mounts}}
  [{{.Type}}] {{.Source}} -> {{.Destination}} ({{if .RW}}rw{{else}}ro{{end}}){{end}}' CONTAINER

Label Enumeration

# All labels formatted as key=value
docker inspect --format='Labels:{{range $k, $v := .Config.Labels}}
  {{$k}} = {{$v}}{{end}}' CONTAINER

Container List on a Network

# All containers on a network with their IPs
docker network inspect --format='Containers on {{.Name}}:{{range .Containers}}
  {{.Name}} ({{.IPv4Address}}){{end}}' NETWORK

IPAM Configuration

# All subnet/gateway pairs for a network
docker network inspect --format='IPAM:{{range .IPAM.Config}}
  Subnet:  {{.Subnet}}
  Gateway: {{.Gateway}}{{end}}' NETWORK

---

Nested Map Access with index

Access Label with Dots in Key Name

# Labels with dots MUST use index function
docker inspect --format='{{index .Config.Labels "com.docker.compose.project"}}' CONTAINER
docker inspect --format='{{index .Config.Labels "org.opencontainers.image.version"}}' CONTAINER

Access Specific Port Binding

# Get host port for a specific container port
docker inspect --format='{{(index (index .NetworkSettings.Ports "8080/tcp") 0).HostPort}}' CONTAINER

# With nil guard (port may not be mapped)
docker inspect --format='{{if index .NetworkSettings.Ports "80/tcp"}}{{(index (index .NetworkSettings.Ports "80/tcp") 0).HostPort}}{{else}}not mapped{{end}}' CONTAINER

Access Specific Network Configuration

# Get IP for a specific network by name
docker inspect --format='{{(index .NetworkSettings.Networks "bridge").IPAddress}}' CONTAINER

# Get IP for a named network
docker inspect --format='{{(index .NetworkSettings.Networks "mynet").IPAddress}}' CONTAINER

---

Scripting Integration Examples

Container IP Lookup Script

#!/bin/bash
# Get IP addresses for all running containers
for id in $(docker ps -q); do
  name=$(docker inspect --format='{{.Name}}' "$id" | sed 's/^\///')
  ip=$(docker inspect --format='{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' "$id")
  echo "$name: $ip"
done

Health Monitoring Script

#!/bin/bash
# Check health of all containers with healthchecks
docker ps --format '{{.Names}}' | while read name; do
  health=$(docker inspect --format='{{if .State.Health}}{{.State.Health.Status}}{{else}}none{{end}}' "$name")
  if [ "$health" = "unhealthy" ]; then
    echo "ALERT: $name is unhealthy"
    docker inspect --format='{{json .State.Health}}' "$name" | jq '.Log[-1]'
  fi
done

Port Mapping Report

#!/bin/bash
# Report all port mappings across running containers
docker ps --format '{{.Names}}' | while read name; do
  ports=$(docker inspect --format='{{range $p, $conf := .NetworkSettings.Ports}}{{if $conf}}{{$p}}->{{(index $conf 0).HostPort}} {{end}}{{end}}' "$name")
  if [ -n "$ports" ]; then
    echo "$name: $ports"
  fi
done

Resource Limit Audit

#!/bin/bash
# Audit containers without memory limits
docker ps -q | while read id; do
  mem=$(docker inspect --format='{{.HostConfig.Memory}}' "$id")
  name=$(docker inspect --format='{{.Name}}' "$id" | sed 's/^\///')
  if [ "$mem" = "0" ]; then
    echo "WARNING: $name has no memory limit"
  else
    echo "OK: $name limited to $((mem / 1024 / 1024))MB"
  fi
done

Cleanup Script Using Format Output

#!/bin/bash
# Remove containers that exited with non-zero status
docker ps -a --filter status=exited --format '{{.ID}} {{.Names}} {{.Status}}' | while read id name status; do
  exitcode=$(docker inspect --format='{{.State.ExitCode}}' "$id")
  if [ "$exitcode" -ne 0 ]; then
    echo "Removing $name (exit code: $exitcode)"
    docker rm "$id"
  fi
done

---

Combined Format with jq

Pretty-Print Specific Sections

# Pretty-print network settings
docker inspect --format='{{json .NetworkSettings}}' CONTAINER | jq .

# Pretty-print environment as object
docker inspect --format='{{json .Config.Env}}' CONTAINER | jq '.[] | split("=") | {(.[0]): .[1]}'

# Pretty-print mounts
docker inspect --format='{{json .Mounts}}' CONTAINER | jq '.[] | {type, source: .Source, dest: .Destination, rw: .RW}'

# Pretty-print labels
docker inspect --format='{{json .Config.Labels}}' CONTAINER | jq .

Cross-Container Comparison

# Compare images across all running containers
docker ps --format json | jq -r '[.Names, .Image] | @tsv' | sort -k2

# Find containers using the same image
docker ps --format json | jq -s 'group_by(.Image) | .[] | select(length > 1) | {image: .[0].Image, containers: [.[].Names]}'

---

Table Format Best Practices

Custom Table with Headers

# table keyword ALWAYS adds headers automatically
docker ps --format "table {{.Names}}\t{{.Image}}\t{{.Status}}\t{{.Ports}}"

# Output:
# NAMES    IMAGE    STATUS          PORTS
# web      nginx    Up 2 hours      0.0.0.0:80->80/tcp
# db       postgres Up 2 hours      5432/tcp

Without Headers (for Scripting)

# Omit "table" prefix to get raw values without headers
docker ps --format "{{.Names}}\t{{.Image}}\t{{.Status}}"

# Output:
# web    nginx    Up 2 hours
# db     postgres Up 2 hours

Multi-Line Per Entry

# Use println for multi-line output per container
docker ps --format "Container: {{.Names}}\n  Image: {{.Image}}\n  Status: {{.Status}}\n"

---

Windows PowerShell Considerations

# On PowerShell, use double quotes with escaped inner quotes
docker inspect --format="{{.State.Status}}" myapp

# For complex templates, use single quotes (works in PowerShell 7+)
docker inspect --format='{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' myapp

# Alternative: use backtick escaping
docker inspect --format="{{.State.Status}}" myapp

ALWAYS prefer single-quoted --format='...' on Linux/macOS. On Windows CMD, use double quotes. On PowerShell, test both; single quotes work in most cases.

Go Template Format Patterns Reference

Complete catalog of 40+ ready-to-use --format patterns for Docker CLI commands.

ALWAYS copy these patterns verbatim -- they are verified against Docker Engine 24+.

---

docker inspect -- Container Patterns

State & Lifecycle

# P-01: Container status (running, exited, paused, etc.)
docker inspect --format='{{.State.Status}}' CONTAINER

# P-02: Container PID on host
docker inspect --format='{{.State.Pid}}' CONTAINER

# P-03: Running boolean
docker inspect --format='{{.State.Running}}' CONTAINER

# P-04: Exit code
docker inspect --format='{{.State.ExitCode}}' CONTAINER

# P-05: Start time (RFC 3339)
docker inspect --format='{{.State.StartedAt}}' CONTAINER

# P-06: Finish time
docker inspect --format='{{.State.FinishedAt}}' CONTAINER

# P-07: Health check status (with nil guard)
docker inspect --format='{{if .State.Health}}{{.State.Health.Status}}{{else}}no-healthcheck{{end}}' CONTAINER

# P-08: OOM killed boolean
docker inspect --format='{{.State.OOMKilled}}' CONTAINER

# P-09: Restart count
docker inspect --format='{{.RestartCount}}' CONTAINER

# P-10: Restart policy
docker inspect --format='{{.HostConfig.RestartPolicy.Name}}' CONTAINER

Network Information

# P-11: IP address (first network)
docker inspect --format='{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' CONTAINER

# P-12: All networks with IPs
docker inspect --format='{{range $net, $conf := .NetworkSettings.Networks}}{{$net}}={{$conf.IPAddress}} {{end}}' CONTAINER

# P-13: MAC address
docker inspect --format='{{range .NetworkSettings.Networks}}{{.MacAddress}}{{end}}' CONTAINER

# P-14: Gateway
docker inspect --format='{{range .NetworkSettings.Networks}}{{.Gateway}}{{end}}' CONTAINER

# P-15: All port bindings
docker inspect --format='{{range $p, $conf := .NetworkSettings.Ports}}{{$p}} -> {{(index $conf 0).HostPort}}{{println}}{{end}}' CONTAINER

# P-16: Specific port (80/tcp) host mapping
docker inspect --format='{{(index (index .NetworkSettings.Ports "80/tcp") 0).HostPort}}' CONTAINER

# P-17: Network mode
docker inspect --format='{{.HostConfig.NetworkMode}}' CONTAINER

# P-18: DNS servers
docker inspect --format='{{json .HostConfig.Dns}}' CONTAINER

Configuration

# P-19: Image name
docker inspect --format='{{.Config.Image}}' CONTAINER

# P-20: Entrypoint (JSON array)
docker inspect --format='{{json .Config.Entrypoint}}' CONTAINER

# P-21: Command (JSON array)
docker inspect --format='{{json .Config.Cmd}}' CONTAINER

# P-22: Working directory
docker inspect --format='{{.Config.WorkingDir}}' CONTAINER

# P-23: Hostname
docker inspect --format='{{.Config.Hostname}}' CONTAINER

# P-24: Environment variables (one per line)
docker inspect --format='{{range .Config.Env}}{{println .}}{{end}}' CONTAINER

# P-25: All labels (JSON)
docker inspect --format='{{json .Config.Labels}}' CONTAINER

# P-26: Specific label by key
docker inspect --format='{{index .Config.Labels "com.example.version"}}' CONTAINER

# P-27: Exposed ports
docker inspect --format='{{json .Config.ExposedPorts}}' CONTAINER

# P-28: User
docker inspect --format='{{.Config.User}}' CONTAINER

Mounts & Storage

# P-29: All mounts (JSON)
docker inspect --format='{{json .Mounts}}' CONTAINER

# P-30: Mount sources and destinations
docker inspect --format='{{range .Mounts}}{{.Source}} -> {{.Destination}}{{println}}{{end}}' CONTAINER

# P-31: Mount types and names
docker inspect --format='{{range .Mounts}}{{.Type}}: {{.Name}} @ {{.Destination}}{{println}}{{end}}' CONTAINER

# P-32: Log file path
docker inspect --format='{{.LogPath}}' CONTAINER

# P-33: Root filesystem size (use with docker inspect -s)
docker inspect --size --format='{{.SizeRootFs}}' CONTAINER

# P-34: Writable layer size (use with docker inspect -s)
docker inspect --size --format='{{.SizeRw}}' CONTAINER

Resource Limits

# P-35: Memory limit (bytes, 0 = unlimited)
docker inspect --format='{{.HostConfig.Memory}}' CONTAINER

# P-36: CPU shares
docker inspect --format='{{.HostConfig.CpuShares}}' CONTAINER

# P-37: CPU quota and period (NanoCpus)
docker inspect --format='{{.HostConfig.NanoCpus}}' CONTAINER

# P-38: PID limit
docker inspect --format='{{.HostConfig.PidsLimit}}' CONTAINER

---

docker ps Patterns

# P-39: Compact status table
docker ps --format "table {{.Names}}\t{{.Image}}\t{{.Status}}\t{{.Ports}}"

# P-40: Names only (for scripting)
docker ps --format "{{.Names}}"

# P-41: IDs only (equivalent to -q)
docker ps --format "{{.ID}}"

# P-42: Name with state and uptime
docker ps --format "table {{.Names}}\t{{.State}}\t{{.RunningFor}}"

# P-43: With specific label column
docker ps --format "table {{.Names}}\t{{.Label \"app\"}}\t{{.Status}}"

# P-44: With size info (requires -s flag)
docker ps -s --format "table {{.Names}}\t{{.Size}}"

# P-45: With network and mount info
docker ps --format "table {{.Names}}\t{{.Networks}}\t{{.Mounts}}"

# P-46: JSON output (one object per line, native)
docker ps --format json

# P-47: All containers with exit info
docker ps -a --format "table {{.Names}}\t{{.Status}}\t{{.Command}}"

---

docker images Patterns

# P-48: Compact image table
docker images --format "table {{.Repository}}\t{{.Tag}}\t{{.Size}}"

# P-49: Repository:tag pairs (for scripting)
docker images --format "{{.Repository}}:{{.Tag}}"

# P-50: With creation time
docker images --format "table {{.Repository}}\t{{.Tag}}\t{{.CreatedSince}}\t{{.Size}}"

# P-51: With digest
docker images --digests --format "table {{.Repository}}\t{{.Tag}}\t{{.Digest}}"

# P-52: IDs only (equivalent to -q)
docker images --format "{{.ID}}"

# P-53: JSON output
docker images --format json

---

docker stats Patterns

# P-54: CPU and memory overview
docker stats --no-stream --format "table {{.Name}}\t{{.CPUPerc}}\t{{.MemUsage}}\t{{.MemPerc}}"

# P-55: Full resource view
docker stats --no-stream --format "table {{.Name}}\t{{.CPUPerc}}\t{{.MemUsage}}\t{{.NetIO}}\t{{.BlockIO}}\t{{.PIDs}}"

# P-56: Names and CPU only
docker stats --no-stream --format "table {{.Name}}\t{{.CPUPerc}}"

# P-57: Container ID with stats
docker stats --no-stream --format "table {{.Container}}\t{{.Name}}\t{{.CPUPerc}}\t{{.MemPerc}}"

---

docker network Patterns

# P-58: Network listing with driver
docker network ls --format "table {{.Name}}\t{{.Driver}}\t{{.Scope}}"

# P-59: Network IDs only
docker network ls --format "{{.ID}}"

# P-60: Network names only
docker network ls --format "{{.Name}}"

# P-61: Containers on a specific network
docker network inspect --format='{{range .Containers}}{{.Name}} ({{.IPv4Address}}){{println}}{{end}}' NETWORK

# P-62: Network subnet
docker network inspect --format='{{range .IPAM.Config}}{{.Subnet}}{{end}}' NETWORK

# P-63: Network gateway
docker network inspect --format='{{range .IPAM.Config}}{{.Gateway}}{{end}}' NETWORK

---

docker volume Patterns

# P-64: Volume listing with driver
docker volume ls --format "table {{.Name}}\t{{.Driver}}\t{{.Mountpoint}}"

# P-65: Volume names only
docker volume ls --format "{{.Name}}"

# P-66: Volume mount point
docker volume inspect --format='{{.Mountpoint}}' VOLUME

# P-67: Volume labels (JSON)
docker volume inspect --format='{{json .Labels}}' VOLUME

# P-68: Volume creation time
docker volume inspect --format='{{.CreatedAt}}' VOLUME

---

docker system Patterns

# P-69: Disk usage table
docker system df --format "table {{.Type}}\t{{.TotalCount}}\t{{.Size}}\t{{.Reclaimable}}"

# P-70: Server version
docker info --format '{{.ServerVersion}}'

# P-71: Storage driver
docker info --format '{{.Driver}}'

# P-72: Operating system
docker info --format '{{.OperatingSystem}}'

# P-73: Total memory
docker info --format '{{.MemTotal}}'

# P-74: Number of containers
docker info --format 'Running: {{.ContainersRunning}}, Stopped: {{.ContainersStopped}}'

# P-75: Plugins (JSON)
docker info --format '{{json .Plugins}}'

---

docker events Patterns

# P-76: Custom event format
docker events --format '{{.Time}} {{.Type}} {{.Action}} {{.Actor.Attributes.name}}'

# P-77: JSON events
docker events --format '{{json .}}'

---

Pattern Index by Use Case