Command Line Interface

f90nml [OPTIONS] [INPUT_FILE] [OUTPUT_FILE]

# Core options:
-g, --group GROUP          # Specify namelist group to modify
-v, --variable VAR=VALUE   # Specify variable to add or modify
-p, --patch               # Modify existing namelist as patch
-f, --format FORMAT       # Specify output format (json, yaml, nml)
--version                 # Show version information

# Display help
f90nml --help

# Show version
f90nml --version

# Simple file reading (outputs to stdout)
f90nml input.nml

f90nml INPUT_FILE -g GROUP_NAME -v VARIABLE=VALUE [OUTPUT_FILE]

# Multiple variables:
f90nml INPUT_FILE -g GROUP_NAME -v VAR1=VALUE1 -v VAR2=VALUE2

# Modify single variable
f90nml config.nml -g run_params -v timesteps=1000

# Modify multiple variables in same group
f90nml config.nml -g run_params -v timesteps=1000 -v dt=0.01

# Save to specific output file
f90nml input.nml -g physics -v gravity=9.81 modified.nml

# Modify different groups (requires multiple calls)
f90nml temp.nml -g group1 -v param1=100 temp2.nml
f90nml temp2.nml -g group2 -v param2=200 final.nml

# Output formats:
f90nml INPUT_FILE -f json    # Convert to JSON
f90nml INPUT_FILE -f yaml    # Convert to YAML  
f90nml INPUT_FILE -f nml     # Keep as namelist (default)

# Input format auto-detected from extension:
# .json  -> JSON input
# .yaml  -> YAML input  
# .nml   -> Namelist input (default)

# Convert namelist to JSON
f90nml config.nml -f json > config.json

# Convert namelist to YAML
f90nml config.nml -f yaml > config.yaml

# Convert JSON back to namelist
f90nml config.json config.nml

# Convert with modification
f90nml input.nml -g params -v value=42 -f json > modified.json

# Pipeline processing
f90nml input.nml -f json | jq '.params.timesteps = 2000' | f90nml -f nml > output.nml

f90nml INPUT_FILE -p -g GROUP -v VARIABLE=VALUE [OUTPUT_FILE]

# Patch mode preserves:
# - Original formatting and indentation
# - Comments and whitespace
# - Variable ordering
# - Only modifies specified values

# Patch single value (creates input.nml~)
f90nml config.nml -p -g run_config -v timesteps=2000

# Patch with specific output
f90nml config.nml -p -g run_config -v timesteps=2000 patched.nml

# Patch multiple variables
f90nml model.nml -p -g physics -v gravity=9.81 -v viscosity=1e-5 updated.nml

# Patch with format conversion
f90nml input.nml -p -g params -v debug=.true. -f json > patched.json

# Script for parameter sweep
for timesteps in 100 500 1000 2000; do
    f90nml base.nml -g run_config -v timesteps=$timesteps run_${timesteps}.nml
done

# Create environment-specific configs
f90nml base.nml -g io -v output_dir="/scratch/prod" production.nml
f90nml base.nml -g io -v output_dir="/tmp/test" -g debug -v verbose=.true. test.nml

# Convert, modify, convert back
f90nml config.nml -f json \
  | jq '.run_params.timesteps = 5000' \
  | f90nml -f nml > modified.nml

# Process multiple files
for file in configs/*.nml; do
    basename=$(basename "$file" .nml)
    f90nml "$file" -g params -v threads=8 "modified_${basename}.nml"
done

# File not found
f90nml nonexistent.nml
# Output: f90nml: error: Cannot read file 'nonexistent.nml'
# Exit code: 1

# Invalid group name
f90nml config.nml -g nonexistent_group -v param=value
# Output: Adds new group 'nonexistent_group' with param=value

# Invalid variable syntax
f90nml config.nml -g params -v "invalid syntax"
# Output: f90nml: error: Variable must be in format 'NAME=VALUE'
# Exit code: 1

# Unsupported format
f90nml config.nml -f xml
# Output: f90nml: error: format must be one of: json, yaml, nml
# Exit code: 1

# Write permission error
f90nml config.nml -g params -v test=1 /read-only/output.nml
# Output: f90nml: error: Permission denied: '/read-only/output.nml'
# Exit code: 1

#!/bin/bash
#SBATCH --job-name=simulation
#SBATCH --ntasks=64

# Modify namelist for this job
f90nml base_config.nml \
  -g parallel -v nprocs=64 \
  -g io -v output_dir="$SCRATCH/run_$SLURM_JOB_ID" \
  job_config.nml

# Run simulation
mpirun -n 64 ./simulation job_config.nml

FROM scientific/base
COPY base_config.nml /app/
WORKDIR /app

# Configure at runtime
ENTRYPOINT ["sh", "-c", "f90nml base_config.nml -g runtime -v threads=$THREADS -g io -v data_dir=$DATA_DIR config.nml && ./simulation config.nml"]

# .github/workflows/test.yml
steps:
  - name: Generate test configurations
    run: |
      f90nml base.nml -g test -v mode=fast -g io -v output_dir=./test_output fast_test.nml
      f90nml base.nml -g test -v mode=thorough -g io -v output_dir=./full_test thorough_test.nml
  
  - name: Run tests
    run: |
      ./run_tests.sh fast_test.nml
      ./run_tests.sh thorough_test.nml

# generate_config.sh
#!/bin/bash
TEMPLATE="template.nml"
OUTPUT="$1"
ENVIRONMENT="$2"

case "$ENVIRONMENT" in
  "production")
    f90nml "$TEMPLATE" \
      -g runtime -v debug=.false. \
      -g io -v output_dir="/data/production" \
      -g performance -v optimization=high \
      "$OUTPUT"
    ;;
  "development")
    f90nml "$TEMPLATE" \
      -g runtime -v debug=.true. \
      -g io -v output_dir="/tmp/dev" \
      -g performance -v optimization=none \
      "$OUTPUT"
    ;;
esac

# Install with YAML support
pip install f90nml[yaml]

# Use YAML format
f90nml config.nml -f yaml > config.yaml
f90nml config.yaml -f nml > config.nml

f90nml config.nml -f yaml
# Output: f90nml: error: YAML support requires PyYAML library
# Exit code: 1