Table of Contents

Docker Command Formatting

Docker provides powerful formatting options for customizing command output using Go template syntax. This allows you to display only the information you need in a clean, readable format.

Why Use Custom Formatting?

  • Improved readability - Show only relevant information
  • Better automation - Extract specific data for scripts
  • Consistent output - Standardize format across environments
  • Space efficiency - Reduce terminal clutter
  • Integration friendly - Easily parse output in CI/CD pipelines

Format docker ps Output

The docker ps --format command allows formatting of the command's output by specifying a Go template string.

Available Template Variables

  • Names: {{.Names}} - Container name
  • ID: {{.ID}} - Container ID (short)
  • Image: {{.Image}} - Image name and tag
  • Command: {{.Command}} - Command being executed
  • Created: {{.CreatedAt}} - Creation timestamp
  • RunningFor: {{.RunningFor}} - Time since creation
  • Status: {{.Status}} - Current container status
  • Ports: {{.Ports}} - Published ports
  • Size: {{.Size}} - Container size
  • Labels: {{.Labels}} - Container labels
  • Mounts: {{.Mounts}} - Volume mounts
  • Networks: {{.Networks}} - Connected networks

Basic Examples

# Simple table format
docker ps --format "table {{.ID}}\t{{.Image}}\t{{.Names}}\t{{.Status}}"

Output:

CONTAINER ID   IMAGE                          NAMES              STATUS
0ebc7a0771fe   immauss/openvas:latest         openvas            Exited (143) 6 weeks ago
676c1497334b   weatherapp:0.0.1               heuristic_panini   Created
81320d86dd52   python_wx:1.0.1                python_wx          Exited (137) 4 months ago
b84ed4fe4739   rabbitmq:3-management-alpine   rabbitmq           Exited (0) 4 months ago

Advanced Examples

# Show containers with ports and running time
docker ps --format "table {{.Names}}\t{{.Image}}\t{{.Ports}}\t{{.RunningFor}}"

# Compact view for scripts
docker ps --format "{{.Names}}:{{.Status}}"

# Detailed view with creation time
docker ps -a --format "table {{.Names}}\t{{.Image}}\t{{.Status}}\t{{.CreatedAt}}\t{{.Size}}"

# JSON-like output for parsing
docker ps --format "{{json .}}"

# Custom headers
docker ps --format "table {{.Names}}\t{{.Image}}\t{{.Status}}" --no-trunc

Filtering with Formatting

# Show only running containers
docker ps --filter "status=running" --format "table {{.Names}}\t{{.Image}}\t{{.Ports}}"

# Show containers from specific image
docker ps --filter "ancestor=nginx" --format "{{.Names}}: {{.Ports}}"

# Show containers with specific label
docker ps --filter "label=environment=production" --format "table {{.Names}}\t{{.Status}}"

Format Other Docker Commands

Docker Images

# Available template variables for docker images
# {{.Repository}}, {{.Tag}}, {{.ID}}, {{.CreatedAt}}, {{.Size}}

# Custom image listing
docker images --format "table {{.Repository}}\t{{.Tag}}\t{{.ID}}\t{{.Size}}"

# Show only image names and sizes
docker images --format "{{.Repository}}:{{.Tag}} - {{.Size}}"

# JSON output for all image data
docker images --format "{{json .}}"

Docker Networks

# Available template variables for docker network
# {{.ID}}, {{.Name}}, {{.Driver}}, {{.Scope}}, {{.IPv4}}, {{.IPv6}}

# List networks with driver info
docker network ls --format "table {{.Name}}\t{{.Driver}}\t{{.Scope}}"

# Simple network listing
docker network ls --format "{{.Name}}: {{.Driver}}"

Docker Volumes

# Available template variables for docker volume
# {{.Name}}, {{.Driver}}, {{.Mountpoint}}

# List volumes with mount points
docker volume ls --format "table {{.Name}}\t{{.Driver}}\t{{.Mountpoint}}"

Configuration Methods

Method 1: Docker Config File

Create or edit the Docker configuration file:

# Create config directory if it doesn't exist
mkdir -p ~/.docker

# Edit configuration file
vi ~/.docker/config.json

Add the following configuration:

{
  "psFormat": "table {{.Names}}\\t{{.Image}}\\t{{.Status}}\\t{{.Ports}}",
  "imagesFormat": "table {{.Repository}}\\t{{.Tag}}\\t{{.ID}}\\t{{.Size}}",
  "statsFormat": "table {{.Container}}\\t{{.CPUPerc}}\\t{{.MemUsage}}",
  "networksFormat": "table {{.Name}}\\t{{.Driver}}\\t{{.Scope}}"
}

Method 2: Shell Aliases

Add to your .bashrc or .zshrc:

# Docker formatting aliases
alias dps='docker ps --format "table {{.Names}}\t{{.Image}}\t{{.Status}}\t{{.Ports}}"'
alias dpsa='docker ps -a --format "table {{.Names}}\t{{.Image}}\t{{.Status}}\t{{.CreatedAt}}"'
alias dimages='docker images --format "table {{.Repository}}\t{{.Tag}}\t{{.Size}}\t{{.CreatedAt}}"'
alias dnetworks='docker network ls --format "table {{.Name}}\t{{.Driver}}\t{{.Scope}}"'
alias dvolumes='docker volume ls --format "table {{.Name}}\t{{.Driver}}"'

# Reload shell configuration
source ~/.bashrc  # or ~/.zshrc

Method 3: Environment Variables

# Set default format via environment variable
export DOCKER_CLI_EXPERIMENTAL=enabled
export DOCKER_PS_FORMAT="table {{.Names}}\t{{.Image}}\t{{.Status}}\t{{.Ports}}"

# Add to shell profile for persistence
echo 'export DOCKER_PS_FORMAT="table {{.Names}}\t{{.Image}}\t{{.Status}}\t{{.Ports}}"' >> ~/.bashrc

Practical Use Cases

For Monitoring

# Monitor resource usage
docker stats --format "table {{.Container}}\t{{.CPUPerc}}\t{{.MemUsage}}\t{{.NetIO}}"

# Quick health check
docker ps --format "{{.Names}}: {{.Status}}" | grep -v "Up"

For Automation/Scripts

# Get container IDs for cleanup
CONTAINER_IDS=$(docker ps -q --filter "status=exited")

# Extract specific information
docker ps --format "{{.Names}},{{.Ports}}" > containers.csv

# Get running containers as JSON for processing
docker ps --format "{{json .}}" | jq '.Names'

For Development

# Show development containers only
docker ps --filter "label=env=development" --format "table {{.Names}}\t{{.Ports}}\t{{.Status}}"

# Quick port mapping overview
docker ps --format "{{.Names}}: {{.Ports}}" | grep -E ":[0-9]+"

Advanced Formatting

Conditional Logic

# Show status with color indicators (requires additional processing)
docker ps --format "{{.Names}}: {{.Status}}" | sed 's/Up/✅ Up/g; s/Exited/❌ Exited/g'

# Custom date formatting
docker ps -a --format "table {{.Names}}\t{{.Image}}\t{{.Status}}\t{{.CreatedAt}}" --no-trunc

Combining with Other Tools

# Pipe to column for better alignment
docker ps --format "{{.Names}} {{.Image}} {{.Status}}" | column -t

# Use with jq for JSON processing
docker ps --format "{{json .}}" | jq -r '.Names + ": " + .Status'

# Integration with watch for live monitoring
watch 'docker ps --format "table {{.Names}}\t{{.CPUPerc}}\t{{.MemUsage}}"'

Troubleshooting

Common Issues

  1. Escaping backslashes in config.json:

    // Correct
{"psFormat": "table {{.Names}}\\t{{.Image}}"}

// Incorrect
{"psFormat": "table {{.Names}}\t{{.Image}}"}

  2. Template variable case sensitivity:

    # Correct
{{.Names}}

# Incorrect
{{.names}}

  3. Missing table keyword:

    # With headers
docker ps --format "table {{.Names}}\t{{.Status}}"

# Without headers
docker ps --format "{{.Names}}\t{{.Status}}"

Validation

# Test configuration syntax
docker ps --format "table {{.Names}}\t{{.Image}}" --limit 1

# Check config file syntax
cat ~/.docker/config.json | jq .

# Verify template variables
docker ps --format "{{json .}}" | jq keys

This comprehensive guide provides everything needed to effectively customize Docker command output formatting.

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