f_dump_nc4_metadata.f90 File Reference

Read a NetCDF-4 file and print all metadata including user-defined types. More...

Functions/Subroutines
program	f_dump_nc4_metadata
character(len=nf90_max_name) function	type_name (ncid, xtype)

Detailed Description

Read a NetCDF-4 file and print all metadata including user-defined types.

Fortran equivalent of dump_nc4_metadata.c. Reads a filename from the command line, opens the file, and prints all metadata:

• User-defined types (enum, opaque)
• All dimensions (name and length, noting unlimited dimensions)
• All global attributes (name, type, and value)
• All variables (name, type, dimensions, and attributes)
• Groups (recursively)

Note: Fortran does not handle VLEN, String, or Compound types portably, so those type classes are reported by name only without detail.

Learning Objectives:

• Use nf90_inq_typeids() to discover user-defined types
• Use nf90_inq_user_type() to determine type class (enum, opaque, compound, vlen)
• Use nf90_inq_enum(), nf90_inq_enum_member(), nf90_inq_opaque()
• Use nf90_inq_grps() to discover groups and traverse hierarchies recursively
• Build a generic metadata inspection tool for NetCDF-4/HDF5 files

Key Concepts:

• User-Defined Types: NetCDF-4 supports enum, opaque, compound, and vlen types; Fortran handles enum and opaque well but has limited compound/vlen support
• Type Class Discovery: nf90_inq_user_type() returns the type class
• Group Hierarchy: nf90_inq_grps() returns child group IDs; recurse to traverse
• Recursive Traversal: Process root group, then recurse into each child group
• NF90_GLOBAL: Used for file-level and group-level attribute access

Prerequisites:

• f_dump_classic_metadata.f90 - Classic metadata inspection (no groups/types)
• f_user_types.f90 - Creating files with user-defined types

Related Examples:

• dump_nc4_metadata.c - C equivalent (handles all four user-defined type classes)
• f_dump_classic_metadata.f90 - Simpler classic-format version
• f_groups.f90 - Creates files with group hierarchies
• f_user_types.f90 - Creates files with enum and opaque types

Compilation:

gfortran -o f_dump_nc4_metadata f_dump_nc4_metadata.f90 -lnetcdff -lnetcdf

Usage:

./f_dump_nc4_metadata f_user_types.nc

Expected Output: Prints all metadata from the specified NetCDF-4 file:

• User-defined types with class, name, and member details
• Dimensions with names and lengths (unlimited flagged)
• Global attributes with names, types, and values
• Variables with names, types, dimensions, and per-variable attributes
• Groups (recursively) with their own types, dimensions, variables, and 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_nc4_metadata()

program f_dump_nc4_metadata

type_name()

character(len=nf90_max_name) function f_dump_nc4_metadata::type_name	(	integer, intent(in)	ncid,
		integer, intent(in)	xtype
	)