f_dump_classic_metadata.f90 File Reference

Read a NetCDF file and print all metadata (Fortran) More...

Functions/Subroutines
program	f_dump_classic_metadata
character(len=10) function	type_name (xtype)

Detailed Description

Read a NetCDF file and print all metadata (Fortran)

This example demonstrates how to use the NetCDF Fortran inquiry functions to discover and print all metadata in a NetCDF file without prior knowledge of its contents. It reads a filename from the command line, opens the file, and prints:

• All dimensions (name and length, noting unlimited dimensions)
• All global attributes (name, type, and value)
• All variables (name, type, dimensions, and attributes)

This is a useful pattern for building tools that inspect arbitrary NetCDF files.

Learning Objectives:

• Use nf90_inquire() to discover file structure without prior knowledge
• Iterate over dimensions with nf90_inquire_dimension() and detect unlimited
• Iterate over variables with nf90_inquire_variable() to get type, shape, and attribute count
• Iterate over attributes with nf90_inq_attname() and nf90_inquire_attribute()
• Read attribute values of different types (text, numeric, arrays)
• Handle unlimited dimensions specially in output
• Accept command-line arguments in Fortran with get_command_argument()

Key Concepts:

• Inquiry Functions: nf90_inquire*() family discovers file contents at runtime
• Variable Iteration: Loop from varid=1 to nvars to visit all variables
• Attribute Iteration: Loop from attnum=1 to natts for each variable or NF90_GLOBAL
• Type Discovery: nf90_inquire_attribute() returns xtype for proper interpretation
• NF90_GLOBAL: Special varid constant for accessing global (file-level) attributes
• Command-Line Arguments: get_command_argument() for Fortran 2003+ input
• Generic Tool Pattern: Read structure first, then interpret — enables tools that work on any NetCDF file regardless of contents

Prerequisites:

• f_simple_2D.f90 - Basic Fortran NetCDF operations
• f_coord_vars.f90 - Understanding dimensions, variables, and attributes

Related Examples:

• dump_classic_metadata.c - C equivalent
• f_dump_nc4_metadata.f90 - Extended version with NetCDF-4 groups and user types
• f_coord_vars.f90 - Creates a file suitable for inspection with this tool

Compilation:

gfortran -o f_dump_classic_metadata \
  f_dump_classic_metadata.f90 -lnetcdff -lnetcdf

Usage:

./f_dump_classic_metadata f_coord_vars.nc

Expected Output: Prints all metadata from the specified file:

• Dimensions with names and lengths (unlimited flagged)
• Global attributes with names, types, and values
• Variables with names, types, dimension lists, and per-variable attributes

Note

Companion code for "The NetCDF Developer's Handbook: The Authoritative Guide to Writing High-Performance Programs for Scientific Data Management, Second Edition" (https://www.amazon.com/dp/B0H7Q1Z75L)

Author

Edward Hartnett, Intelligent Data Design, Inc.

Date

2026

Function/Subroutine Documentation

f_dump_classic_metadata()

program f_dump_classic_metadata

type_name()

character(len=10) function f_dump_classic_metadata::type_name

(

integer, intent(in)

xtype

)