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Option Formats

Learn all the ways users can specify options when running your Argus-powered programs.

Overview​

Argus supports flexible command-line formats, allowing users to specify options in multiple ways. This flexibility accommodates different user preferences and command-line conventions.

Basic Format Patterns​

PatternDescriptionExample
Long optionsDouble dash + name--verbose, --output=file.txt
Short optionsSingle dash + character-v, -o file.txt
Combined shortMultiple flags together-vxf (same as -v -x -f)
PositionalNo prefix, order mattersinput.txt output.txt
Option terminator-- ends option parsingprogram -- --not-an-option

Long Options Format​

Long options use descriptive names with double dashes (--).

# Value after space
./program --output result.txt
./program --port 8080
./program --quality 0.8
./program --debug true

When to use: Most readable, works with all option types.

Short Options Format​

Short options use single characters with single dashes (-).

# Each option separate
./program -v -o result.txt -p 8080
./program -v -f -o output.txt input.txt

When to use: Clear separation, works with all types.

Mixed Format Examples​

Users can mix different formats in the same command:

# All equivalent commands
./program --verbose --output=result.txt input.txt
./program -v --output result.txt input.txt  
./program --verbose -o result.txt input.txt
./program -v -oresult.txt input.txt
./program -vo result.txt input.txt
./program -voresult.txt input.txt

Positional Arguments​

Positional arguments are provided without option prefixes, processed in order.

Basic Positional Usage​

# Required positionals
./program input.txt output.txt

# Mixed with options (any order)
./program --verbose input.txt --output-format json output.txt
./program input.txt --verbose output.txt --format json

Optional Positionals​

# Optional positionals can be omitted
./program input.txt              # Uses default for optional args
./program input.txt output.txt   # Provides optional arg
./program input.txt output.txt 1024  # Provides all args

Special Cases and Edge Cases​

Negative Numbers​

Argus intelligently handles negative numbers vs options:

# These are treated as values, not options
./program --threshold -5.2
./program --coordinates -10 -20
./program input.txt -42    # Positional negative number

Rule: If a positional option expects a number, -123 is treated as a negative number, not an option.

Option Terminator (--)​

The double dash -- stops option parsing - everything after is positional:

# Everything after -- is positional
./program --verbose -- --not-an-option file-with-dashes.txt
./program -v -- -x -y -z   # -x -y -z are positional arguments

Use cases:

  • Files starting with dashes
  • Passing arguments to sub-processes
  • Avoiding option conflicts

Ambiguous Cases​

When input could be interpreted multiple ways:

# Ambiguous: is "file.txt" a value for --output or a positional?
./program --output file.txt another.txt

# Unambiguous with equals
./program --output=file.txt another.txt

# Unambiguous with --
./program --output -- file.txt another.txt

Collection Formats​

For array and map options, Argus supports multiple input methods:

Array Options​

# Each occurrence adds to array
./program --tags web --tags api --tags backend
./program -t web -t api -t backend

Map Options​

# Each occurrence adds key-value pair
./program --env USER=alice --env HOME=/home/alice
./program -e USER=alice -e HOME=/home/alice

Real-World Examples​

Here are complete command-line examples showing different patterns:

Simple File Processor​

# Basic usage
./file-processor input.txt

# With options  
./file-processor --verbose --output=/tmp input.txt
./file-processor -v -o /tmp input.txt
./file-processor -vo /tmp input.txt

# Complex example
./file-processor -v --format=json --threads=4 input.txt output.txt

Git-Style Tool​

# Subcommands with options
./tool add --force file.txt
./tool commit --message="Fix bug" --author="John Doe"
./tool push --tags --dry-run origin main

# Mixed formats
./tool add -f file.txt
./tool commit -m "Fix bug" --author="John Doe"

Build Tool​

# Array and map options
./builder --targets=lib,bin,tests --env=DEBUG=1,OPT=2
./builder -t lib,bin -t tests -e DEBUG=1 -e OPT=2

# With option terminator
./builder --verbose -- --enable-debug --target=all

Format Validation​

Argus automatically validates option formats and provides helpful errors:

# Missing value
$ ./program --output
program: Missing value for option: '--output'

# Invalid format  
$ ./program --port=abc
program: Invalid value 'abc': expected number

# Unknown option
$ ./program --unknow
program: Unknown option: '--unknow'

Best Practices for Users​

# ✅ Clear and readable
./program --verbose --output=result.txt input.txt

# ✅ Compact but clear
./program -vo result.txt input.txt

# ✅ Unambiguous with complex args
./program --config=app.conf -- input-with-dashes.txt

Avoid Confusion​

# ❌ Potentially confusing
./program --output result.txt result2.txt  # Which is positional?

# ✅ Better alternatives
./program --output=result.txt result2.txt
./program --output result.txt -- result2.txt

Compatibility Notes​

Argus format support is designed to be compatible with common CLI conventions:

  • GNU-style long options: --option=value
  • POSIX-style short options: -o value, -ovalue
  • BSD-style flag combining: -abc
  • Git-style subcommands: program command --option

This ensures users familiar with standard Unix tools will find Argus programs intuitive to use.

What's Next?​

Now that you understand how users can format their commands, learn how to:

Pro Tip

The format flexibility is automatic - you don't need to code for different formats. Define your options once, and Argus handles all these input variations!